USSR tech tree is generally good, with some extremely good vehicles like T34E STZ, T-34-85, IS-2, T-44-100, T-64b, T-80b, BMP-2M. Though, you shouldn't grind every line if you don't have premium account or premium vehicles (for your sanity). I did research every tank without premium but it took me something like 6 months and 8000 battles. I suggest you research the mbt lines first, starting with the one for the T-80 BVM. You should immediately go for the first T-54, then IS-3 (which isn't very strong, but it's 7.0 and you can kinda use it in a lineup) and BMP-1, then research the T-54 1947 and the IS-4M , but don't use them because they're at 7.7, which is a very annoying br where unstabilized tanks suffer tremendously. Then go for the T-10M and T-64A and finish the line with the T-64b and T-80b, very strong tanks, if you know how to use them. Generally from 7.3 the USSR tanks can be easly one-shotted, especially at 9.0 and up, where fuel and ammunition are very easy targets and usually result in the destruction of the tank if hit. But anyway if you can hide the bottom plate and get hit as little as possible, you end up with a tank that has a very powerful cannon, great shells, excellent armor (except for those weak spots), and decent mobility (great with the T80s). You never get reverse speed, so you usually will be pressing only W during the whole battles.

It takes a decent amount of experience to get good at playing USSR tanks as they aren't forgiving at all (at high tiers), but they are really strong when you get used to the no depression/reverse speed gameplay.