Hi OofMs,
I've had MS for close to two decades (I too was diagnosed at 21). I've been on numerous treatments (Avonex, Copaxone, and now Tysabri). I would recommend asking your doctor what he thinks would be your best bet. Ocrevus is the latest and people are doing well with it. The important thing is to get started on something sooner than later. While a lot of people fear PML (the "brain virus thing"😉, the chances are really pretty low and most of those cases happened before they knew it could be a problem. They actually have much better tests know and you will be monitored (you can read more on that here: https://multiplesclerosis.net/living-with-ms/pml-jc-virus-misconceptions/).
When choosing one of the disease modifying drugs (DMDs), the most important thing is to choose something you can tolerate and stick with. No everyone can inject them selves, some people hate IVs, etc. As for tolerating them, you won't know until you try them. That's the other thing, you may need to try several before you find out what works for you (or you may not). Good luck and remember that the most important thing, is to get on one.