I was surprised at how cheap LiPo's are. They sound a bit scary and it's new terminology 2S 4C etc. but not that complicated, plenty of sites and threads explaining it. Though you are on a budget perhaps they are still worth a look. But you will need a charger (and some on ebay ship without a mains charger) and a safety bag to comply with regulations. Also a fuse is mandatory in a LiPo system (but I'd fit one even if not).