If you already have an aviation contract, don't waste your money - helicopter lessons are EXPENSIVE. Once you finish TBS and if there is a wait (there almost always is) you can ask for TAD orders to a Marine Reserve helicopter squadron. Likewise, if there is a wait between primary and advanced helos, you can also go TAD to a Marine Reserve helo squadron. There you will get some stick time for free in 53's, 46's or skids instead of a little Robinson R-22 - and the Majors and LtCols love having 2nd Lt's around - you will have a lot of fun.
Good Luck.