Hi Tarrant.
My particular advice it’s:
Go to dojo and complete it, try some offline matches against the cpu to get along the combo system, and then visit Ifilament’s guide, a great guide for all type of players 
When you hit online, I recomend you exibition. It allows you to rematch really fast than lobby or ranked leagues.
Unfortunately, I can’t answer you about your problem with the greyed characters. Maybe @rukizzel or @TempusChaoti could help you with that