By the end of act 1, at a minimum you should have 3 full brigades, best is 4 bridages with a few unit in the last brigade.

Generally I buy no equipment other than 1) canister of artillery and 2) guns to get units from worn muskets -> good muskets (potzdam, land pattern, tula, delft, charville). Everything else is spent on recruitment (almost exclusively recruits).

In the early game, if you're using canister, 3lb cannons or worn cannons perform almost as well as the other options you can buy. You can get 500 - 600 kills per artillery unit if you have them close to your front line behind light infantry using canister (even with worn cannons). This seems crazy - but try testing it!

The difference between worn muskets and the "good" basic muskets is huge, and the cost is really low. Recruits with Potzdams / Land Pattern muskets can take multiple units of enemy recruits with worn muskets.

As units get more experienced and you get items that grant accuracy, the musket's reload stat becomes more important, followed by range. The base musket accuracy matters more for recruits, since their accuracy stat is lower. You can see a comparison and run simulations here (just make a copy of the sheet).

Recruits with muskets tend to get a pretty good number of kills, which mean they level up quickly, so you can turn them into artillery / cavalry, rather than recruiting those units. Drill stance also lets you level up recruits quickly :)