I do iOS dev as a side-hobby too (https://jacobdoescode.com/)

People are right it isn’t anywhere near a salary, but I have fun and it has opened job opportunities too

For marketing, I found /r/Apple very receptive to self promotion posts - just make sure you meet the criteria. You can also do a discount period and advertise on /r/AppHookup. Last Black Friday I reduced a $2 to 29c (lowest allowed price) and made just shy of $500, and it boosted my place in the store search

Best of luck!