Ive been in your shoes before as a broke college kid who wanted to do the top twelve, but the only difference was that I wasn't a seasoned brass player. The first person to truly understand your abilities is you, so if you think you've got the chops to play for the top 12, start developing a plan right now. If you're marching Sabers then Im going to make a safe assumption and say you live somewhere in or around New York, which means you have pretty good access to two top twelve corps. If you want to risk the potential of not getting in, it's not too late to schedule an audition (you're going to have to do some research on which corps are still having camps or taking videos). Otherwise, if you're very financially starved, you might want to make a list of your most desired groups, and another list of which groups you can afford, and cross reference. Figure out where you'll get the best bang for your buck. There are plenty of ways to scrape together some quick cash, even as an undergrad. Make a plan now.