Help me invest ~100 euros

Heyyo!

　After summer and everything I got some money left, not really planning on buying anything, well maybe a phone. I'm a person that saves money, so I wouldn't want to do anything crazy, I thought about some options and I came to a conclusion that I am ready to 'donate' 100 euros on trying to get more. I thought I could maybe invest in BTC or some other cryptocurrency, really considering on investing in BTC since it's price is rocketing up. It all seems cool and easy, but I don't really know how and where to do that - like invest in stocks or just load up a wallet, and if, then where? : D
　I also thought about maybe buying a phone for some 300, 400 euros and then refunding it, but that's not really what I'd like to do cuz yeah, It'd be cool if I got a new phone, but it isn't really necessary for me to get a new one right now, and also it seems for me that refunding phones is usually hard and often ends up non-successful.
　I also thought about reselling stuff, cuz I'm pretty good at that. I'm currently searching for stuff that has hight resell value. I'm currently making some money doing this too.
　As some might know, I have opened a Spotify service and am working on support as much as I can, so don't call me a lazy fuck who wants easy money or something like that ;d.

Please post your recommendations below.
And as always - if you don't have anything logical to say, don't say it - don't shitpost!
Thanks!