Hello there
After seven years of building decks, I found a good average solution as a deck template to start building. Naturally, after doing that, I tend to playtest the deck 4-5 times and adjust it depending on the feel and the needs of it.
For me, key is that the mana base + ramp comes to 50 cards. This seems a lot, but I tend to look if I can find ramp that fits the deck, or is particulary good in the deck and might be ideally also fulfilling other purposes. For the avg. mana base, I calculate 30 lands+ mana value of the commander + 1 added land. This means, with a commander of mana value 5, the total land count would be 36. After that, I build the ramp package. If it is, for example, 36 lands, then I do 14 ramp, so that I come to the total value of 50. Ideally, it is even better if you can add + 1 ramp card, that seems to work the best (total Land and Ramp count: 51). At least that is where most sweet-spots lie in most of my decks.
After building the mana and ramp base, I look for at least 12+ card draw options, at least 1 mass removal, at least 4 recursion and 4 protection options and around 5 target removal (I tend to run a fairly low amout because my playstyle is tweaked more to let everybody do their thing; having a fun evening and more games).The rest are cards that just specifically work with the commander.
So in the case of the hypothetical 5cmc commander it would look like this:
36x Lands
14x Ramp
12x Card Draw
5x Target Removal
1x Mass Removal
4x Recursion
4x Protection
76 Cards + Commander 77 Cards.
The rest of the 23 cards are just specific to the commander deck.
I hope it helps.
Cheers!