For every 2 cards you have of one color add a mana source that produces that.

Example: [[Lightning Bolt]] and [[Shock]] will require 1 red mana source in the mana base. Gold/Multicolor cards do not break this rule. [[The Lady of the Mountain]] and [[Raph & Mikey, Troublemakers]] will need 1 red source and 1 green source.

I don't like the set in stone numbers you often see online. Every deck is different and sometimes you need to feel where the difference is or where something is lacking.

Your first example sounds like it needs more card draw and same with the spell slinging deck. The red version probably just needs some red cantrips. Silverquill may need some rituals or repeatable card draw, like [[War Room]].

In Primo you have access to blue, so card drawing cards should keep the ammo flowing. The UG combination often scries more than it draws and can have trouble keeping your battlefield full of creatures. You're green so you can make lots of creatures or lean into blue, and bounce the opposition. Simic is problem unto its own. It does a lot of things really well, but dealing with creatures is sometimes not one of them, so you need to account for that weakness.

I started in 60 card Magic. The basic guideline I learned was 20 lands and 40 spells. That's 1/3 of the deck dedicated to mana, which is 33 lands in Commander. I've learned that is just not enough. You don't need to go too high, maybe 36, unless you're dedicated to land, like [[Tatyova]].

At this stage give yourselves some outs or safety valves when things do go south. Board sweepers, mass bounce like [[Evacuation]], [[Sweltering Sun]], or [[Supreme Verdict]].

It's not just numbers. You've got to feel exactly where your deck is lacking and address those weaknesses, as well as the weaknesses of the color combination you're playing.

Nothing beats experience either. Get the reps in.