There really needs to be more things to buy in duolingo shop. I can only get 3 but I already bought them.
Have you already tried to buy any bonus skills? For example, in french, that you are level 2 at, There are flirting and idioms bonus skills after the first shortcut, whet you will get to it, just click on bonus button and buy an appropriate skill for 30 lingots.
Hope it helps! Good luck!