you can set up a metamask wallet for free so that you can get an address to enter brittufs contests with this link here - https://metamask.io/ then once you've won a bunch for free and if you decide you'd like to breed some to try and make a fancy kitty or something u can put in as much or as little ETH as you like. i started with 100$ worth myself after winning loads from brittuf, i have just over 100 kitties now! whoops! i have bred a few cool fancy cats though, hopefully theyll be worth a bit more down the line.. breeding costs around 5$ if you use 2 of your own cats, or maybe a bit less if you use someone else's sire. putting your cats up for auction also costs a bit of gas but not much more than 30 cents and you can fiddle with the amount of gwei you use to make it a bit cheaper.. also you could check out etherstocks if you'd like to make some eth back a bit faster than kittys, the day trader can make you some nice quick profits if you don't get stuck with a bag..