Wa alaikum salaam
I'll answer based on my knowledge of the rules within the Hanafi madhab. There are finer details you probably don't need to worry about too much, so I'll cover the high level basics.
Besides Surah Fatiha, you should recite at least one long verse or three short verses in each ruku. There are details as to what long and short are, but I recommend you avoid these by choosing three verses. The exception is if you want to recite the last verse of Baqarah for example, which is clearly long, and one I'd highly recommend.
In Hanafi, you are allowed to recite different surahs even within the same ruku. Avoid reciting two surahs, while skipping the one between them. Avoid reciting in reverse order.
I reiterate there might be differences with other madhabs.