If you would like to get into BTC on a budget, consider some cheaper alt coins as an investment and trade (though currently with the recent jump in BTC this has dropped their ratios).
If you have a little more money, consider a 28nm ASIC (if you can get your hands on one within the next 4-6 weeks). Anything longer means the difficulty will be too high and your initial investment will never be returned (unless of course BTC jumps a decent percentage again).