Please don't ignore them. Spellcasters are already stronger than martial classes, this is one way to keep spellcasters in check.

Especially materials with costs (Revivify, etc.)... especially when they are consumed.

https://www.youtube.com/watch?v=nbC74sKKfA0&list=PLQMqiULo_05OupYIohJFqY1UIKMEGWNA2&index=7

Spells require intent and will. The act of casting a spell is big and noticeable (verbal and somatic).

Somatic (S) gestures require a free hand.

Material (M) components require a free hand.. but a focus can handle this. Technically speaking (rules as written), a focus only satisfies the somatic requirements of a spell when the spell has material components.

https://www.dndbeyond.com/forums/dungeons-dragons-discussion/rules-game-mechanics/49286-spellcasting-focus-prevents-somatic-components

" This is an often misunderstood rule. InquisitiveCoder pointed it out though - material component rules only apply to spells with material components. Jeremy Crawford recently stated something like this on one of the WotC streams: "D&D rules are not a physics engine where you need to know everything in order to adjudicate anything." You only need to know the rules that apply to a particular situation. In the case of spellcasting, only the rules for the components listed apply. Without feats or special abilities, you need:

A free hand to do somatic components for S (but not M spells) - an occupied hand, even when occupied by a focus, doesn't meet this requirement (without feats).
A free hand to handle components for M (but not S spells) - this hand my be occupied by your focus, which could be a shield, weapon, or instrument depending on class/subclass.
A single free hand to handle both the material and somatic components for S and M spells - a focus occupied hand works here.

The net of all of this is that without warcaster you need to get a hand free to cast S (but not M) spells." - https://www.dndbeyond.com/forums/dungeons-dragons-discussion/rules-game-mechanics/49286-spellcasting-focus-prevents-somatic-components

Trying to Argue a Spellcasting Focus Satisfies Somatic Requirements of a Spell... It doesn't work.

One could argue this though, this rules say the following (emphasis is mine):

A spellcaster must, have a hand free to access a spell’s material components — or to hold a spellcasting focus — but it can be the same hand that he or she uses to perform somatic components.

Even though the explanation of how a focus works is in the Material section of the spell casting rules, it does spefically state "it can be the same hand that he or she uses to perform somatic components" -- no where in this section does it say the material components are required to satisfy the somatic components of the spell. Even though the somatic rules don't cover what a focus does, the rules state somatic components are fulfilled by the focus. It would be much better if the rules had a section explicitly for spellcastubg focuses instead of having those rules scattered throughout the book. Think about it for a second, Harry Potter uses a wand to satisfy the somatic requirements of a spell when he casts a spell (flicking the wand is the somatic component).

I wanted to contradict myself a bit here and suggest allowing the use of a focus to satisfy the somatic requirements of a spell; When I thought of wizards casting a spell, they were casting the spell from their wand or their staff... That's not necessarily the case once you start digging into artwork. It's a common misconception because a lot of artwork has the caster casting the spell from both of their hands. Typically if the caster is holding something (a staff, a book, a globe), they are using their open hand to cast the spell.

The problem with this argument? Rules indiciate when they apply and the rules surrounding material components (and spellcasting focuses) only apply to spells that require Material components. You only need to satisfy the material components of spells if the material component exists. If you only know the Somatic components of a spell, those require a free hand to cast the spell. Sage Advice ruled specifically mentioned this scenario:

A spellcasting focus can be used in place of a material component only if that component has no cost noted in the spell's description and if that component isn't consumed.

More from Sage Advice:

Another example: a cleric’s holy symbol is emblazoned on her shield. She likes to wade into melee combat with a mace in one hand and a shield in the other. She uses the holy symbol as her spellcasting focus, so she needs to have the shield in hand when she casts a cleric spell that has a material component. If the spell, such as aid, also has a somatic component, she can perform that component with the shield hand and keep holding the mace in the other.

If the same cleric casts cure wounds, she needs to put the mace or the shield away, because that spell doesn’t have a material component but does have a somatic component. She’s going to need a free hand to make the spell’s gestures. If she had the War Caster feat, she could ignore this restriction.

https://dnd.wizards.com/sage-advice/rules-of-spellcasting

War Caster fixes the somatic issue for casters that typically carry a shield (paladins and clerics). This makes the War Caster feat virtually a requirement if a caster wants to use a weapon or a shield and that's absolutely okay -- if there was a feat called "Well Armored" and it gave you +2 AC, a lot of characters would take that and that's essentially what War Caster does:

War Caster
You can perform the somatic components of spells even when you have weapons or a shield in one or both hands.

These requirements impact multiclass characters more because it may require two different types of focuses and an open hand (i.e. not carrying a shield on your wizard).

While these rules may take away some of the fantasy aspects of a character, the rules have ways to get around this (clerics and paladins can use their shield.... hexblades can make their weapon a focus... the War Caster feat exists for a reason). If you were to handwave these rules (Pun intended, I suppose), you're taking away from choices other players made.

There's also a Ruby of the War Mage (this requires attunement):

Ruby of the War Mage
Wonderous Item, common (requires attunement by a spellcaster)

Etched with eldritch runes, this 1-inch-diameter ruby allows you to use a simple or martial weapon as a spellcasting focus for your spells. For this property to work, you must attach the ruby to the weapon by pressing the ruby against it for at least 10 minutes. Thereafter, the ruby can’t be removed unless you detach it as an action or the weapon is destroyed. Not even an antimagic field causes it to fall off. The ruby does fall off the weapon if your attunement to the ruby ends.

So you can take a class feature that does this, take a feat that does this (and more), or use one of your attunement slots to do it. All of these seem perfectly viable and easily done within the rules of the game.

Think about what a Swords bard looks like compared to a traditional bard. A Swords bard is allowed to use their weapon as a focus but a normal bard needs to hold their musical instrument (ironically, they don't need to be playing it... just holding it).

https://www.reddit.com/r/3d6/comments/e8nzmd/onehanded_instrument_for_my_shieldwielding_bard/ https://www.dndbeyond.com/forums/class-forums/bard/125401-one-handed-two-handed-and-versatile-musical

https://www.reddit.com/r/dndnext/comments/4i0zlb/can_a_hand_holding_a_focus_perform_the_somatic/ https://www.dndbeyond.com/forums/dungeons-dragons-discussion/rules-game-mechanics/49286-spellcasting-focus-prevents-somatic-components https://rpg.stackexchange.com/questions/124167/can-i-use-a-hand-holding-a-focus-from-one-class-to-cover-somatic-components-for

https://arcaneeye.com/mechanic-overview/spellcasting-focus-5e/ https://www.dndbeyond.com/forums/dungeons-dragons-discussion/rules-game-mechanics/24830-spellcasting-focus

The easiest way to think of how spellcasting should work: casting a spell always requires an open hand for somatic spells, if a spell requires material components, you need a focus (and sometimes that focus can be a shield, weapon, or something else) but it still requires an open hand. Exceptions to this rule apply, but always assume a free hand is required for casting the spell.

Another rule of thumb: If you want to wield a weapon and/or a shield, you need to have War Caster. Clerics can use their shield as a focus but generally want an open hand to cast their spells, the same goes for the Swords Bard but they use their weapon as their focus instead.

There's some leeway with the somatic requirements of spells because 5e has some loose rules around dropping a weapon with a free action, casting the spell with a free hand, and picking up your weapon as part of your movement. So just because a spell requires a free hand, it doesn't mean you can't have a free hand available during your turn. The same goes for holding a weapon in two hands, you could reasonably remove one hand from the weapon to cast the spell and then grab the weapon again.

Even though you're mechanically doing something to satisfy the rules of the game, it doesn't mean you can't describe what you're doing differently. In the case of dropping your weapon, casting a spell, and picking the weapon back up.. I'd absolutely flavor it as "I stab my polearm into the ground, with my free hand, I cast Guiding Bolt, and reach for my polearm."

For the love of God, just take War Caster if you're looking to cast spells while holding a weapon or a shield.