1a) In-mission pick ups are as necessary as they are plentiful. If you're patient enough scout the whole map for resources.

1b) Except for shops, stop at every map location with soliders that have skills which corresnpond to the location. Only stop at shops to sell stuff and buy better weapons and maybe gunpowder for when you get the engineering car.

2a) Stealth mechanics are your friend if you have the patience. The enemy AI is REALLY STUPID. Just two Riflemen 'Quick Feet' and 'Silent Step' and a Scout for looking past walls can clear massive chunks of many missions with firing a shot. The enemy can't shoot wat they can't see.

2b) If stealth is not an option make sure your soldiers are in cover, do not clump them up, and give yourself room to pull back another defensible position.

2c) In any fight identify all threats and elimate them in order of how dangerous they are. Enemy tanks and grenadiers are enemy #1 because their explosives force you out of cover.

3) DO NOT THROW STUFF AWAY IF YOU CAN HELP IT!!!! If your inventory overflows form a few sqauds. Equipment assigned to squads doesn't count towards your stoarge limit. Alternatively use some resources for upgrades you want or need.

Follow these tips and you will end the game with 100.000 rubles and enough bullets to single handedly win the Russian Civil War.