If you're playing in 36' the way I tend to go for the SU is to build IC and IC only until ~ 38 (any IC that finishes in late 37' will be shifted to big things).
The reason I like building so much IC is because I like to build things for self-indulgence, like STRAT, air transports, paratroopers, and TAC bombers that are entirely unnecessary, but let me have fun. You'll want to have a big gross IC number to build lots of big projects at once - if your intention is for the heaviest IC thing you build to be medium tank divisions, you could probably dispense with building IC as soon as you can build MARM brigades. I shoot to have ~300 IC (post purge) before I begin large-scale military production.
Once you hit 38, throw your IC into big ticket items like planes and medium tanks and Marines (I build 5 divisions of them and use 2 for the Baltic fleet, 2 for the Black Sea Fleet, and 1 for mucking about in the Belorussian Swamps - because Germany will occasionally put troops in there and Marines will make short work of them). Then, once you reach later 39' I start putting out 3x1 arty and 3x1 AT brigades for standard purpose, with HARM (2 HARM tanks + 1 TD) and 4x Garrison divisions for each major city (roughly 9 divisions in total - you can retreat them as cities are lost and plop them in some other city EFFICIENCY! lol) and 1 div of MARM and LARM + Moto-rifle (with SPART/SPRA if possible) running until war starts. I like to tie my medium armor divs to equivalent light armor corps for exploitation.
I like to construct my ARM divisions in the following way: LARM 1 light tank, 2 moto-rifle (add SPART/SPAR as you get them later), for MARM's I build them as 2 medium tanks + 1 motorifle + SPART/SPRA, with a few who hold engineers for eventual river crossings, fort storming, and defensives of said crossed rivers and forts.
Then it's mostly up to how you want to defend. You can try to defend a static line somewhere - at which point you're going to want to mobilize early, pick a spot you like, and just stack all your stuff up there and make sure they never break through (use your medium armor to support spots in the line which are buckling). You can go Tukachevsky and defend indepth, where you put a line of troops in an ideal defensive position and put 2x divs in that territory, and then spread excess troops outwards towards your borders. As the germans attack, your weak 1 div will retreat after fighting a bit (preserve your manpower you're only doing this to cause their unit to incur command delay and burn supplies) - then once the unit occupies the territory all units behind it will simultaneously attack that division. If the fight isn't remotely winnable abort the attack immediately - if it's winnable fight them down so you break an Axis division, and cover the retreat of whatever division you're fighting. The main obstacle to this method of attack is that you MUST NOT allow your forces to retreat into the swamps in Belorussia or you will end up losing them (you need to decide ahead of time which will retreat south and which will retreat northwards). Once the Germans reach your main line of defense, you let them throw themselves at it, and array your tanks on any easily attackable province and SLAM them with tons of Armored attacks in that area - the AI will panic and after a few days will start resassigning troops to that region - so you pick another good spot, and SLAM it with tanks too, and eventually you'll start pushing the Germans back or at least severely hampering their attack progress. Just remember, DON'T let any of your forces go into the swamps in Belorussia, and try not to get anybody encircled - you'll need every division and, possibly, every oz. of man-power. If your tanks start taking damage withdraw them immediately - they're too valuable to let them get bogged down early on. If you end up engaging all of your armor in 41' and it gets stuck in some offensive you wont have the reserve capability to respond.
Other bonus stuff I like tossing around are Submarines (in the black sea, and Baltic sea fleets and even in the arctic ESPECIALLY if Germany takes Norway - because you can virtually blockade Norway and starve out any German divisions there - assuming you took/puppet Finland and research a few submarine engine upgrades (the 1940 tech).
You could also just build a giant fort line and stand behind that - but where is the fun in that?
