I agree with what phil said but want to add a few things. What position do you play and when does your season start? I’m gearing up for my spring season and have been working the oly lifts, heavy deads, and heavy squats for most of the off season. Endurance and speed work starts soon (well, as soon as I stop putting if off. I’m a prop, long runs and interval sprints suck.) If you’re in the pack, I’d work heavy legs and back mostly. Also, you might want to do some mixed work with lifts and sprints. Try doing a set of dumbell snatches or swings and then go right into a hill sprint. It’s killer for building up the ability to move from rucks, mauls, and scrums into sprinting across the field. Search for “litvinov” on here and you’ll find a great article.
If you’re in the back line, I’d work mostly on sprints, breakout speed, avoiding/breaking contact, and making friends with your forwards who’ll be keeping you from getting your face stomped on (also, you may want to practice essential back line skills like missing passes, losing the ball in contact, missing kicks, dressing purdy, perfecting your hair, and keeping your kit clean for an entire match (how do they do that?)).
Either way, your biceps may be your weak point, but building them up ain’t gonna win you games or keep you from getting stomped on the pitch. Work on brute strength and explosive power in the legs and back, it’ll help your game a lot more.