These are your only three options. Buy, download other teamlava games, or master catalogues. I can understand avoiding the first option, but the other two are easy and don't take two lon
g. Just aim to master the 1 min, 2min, and 15 min ones and you'll be almost there in a couple of days.
There's no way to get gems totally for free. Thats the whole point of the gems...to try and get you to pay up!