Buying you a coffee is the better option i think. Though I wont be able to pay as of now (I am a teen. I can't earn). But $2 is reasonable enough to pay when I earn.
Marketplace - I think more people would buy themes and stuff for their blog more than recruitment. Though it makes sense that hashnode is developer centric and recruiting developers on this platform makes sense. I think themes will get you more, quick bucks than recruitment and will be easier to implement.
Training and courses - I would suggest to make use of platforms like lbry and reuse their network to host the courses. It will be easier.
Ads and tracking network is a bad idea.
I think you should charge for premium services.