Comrades are the main currency in the game and the most basic resource. Comrades are produced every second. The number of comrades produced per second can be increased by "trading" potatoes, land, ore, bullets, and placebos. The n-th trade in each category costs 5*(10^3n), so the first trade in each category costs 5,000 of that item, the second costs 5 M, the third costs 5 B, and so on. The number of extra comrades per second per trade in a category can be increased by purchasing researchers. Comrades and comrades per second are both reset upon reaching a new rank.
All resources that can be bought in the game cost comrades, except for science and gold. The potato industry's resources cost 1 comrade, the land industry's cost 2, the ore industry's cost 3, the bullet industry's cost 4, and the placebo industry's cost 5.
Comrades are the most important resource. Once you are past the initial few ranks, you will spend many days waiting to accumulate comrades to complete missions. It is highly recommend you upgrade the "Trading XXX grant extra comrades" researchers as soon as you are able. Prefer to upgrade the higher tier researchers (i.e. Sir Lance Egon for placebos) if you have a choice of more than one. Even though you will buy comrades with potatoes more often, the comrade multiplier for the higher tiers more than makes up for the lower number of purchases.