Hi Frank,
It depends which way you want to go, a) to make your own theme; or b) to use existing ones.
I started hacking Landscape theme and rewrote it inside out (only to find that Hexo doesn't support two blog categories I needed) so I switched to Hugo.
The learning curve is easier with Hugo, another static site generator, because it can generate blank theme - handy if you go a) route.
If you go a) route and just want a simple quick blog, again, will probably be easier to use Hugo since you don't have NPM, dependencies and all that sudo permissions thing (if you set it up npm wrongly and not use nvm). Try both, check out documentation. For me, Hugo is better.
If you're just starting, I would also advise not to jump into hosting at GitHub, but host on normal server (ideally your own Ubuntu/Nginx such as Digital Ocean), because:
1) there's additional setup needed to set up GitHub hosting, that's extra difficulty. However, documentation is not the best on Hexo.
2) you don't really see actual server, files etc, but you need the exposure to learn. There are excellent tutorials step-by-step on Digital Ocean for pretty much every task, for example. Hugo documentation is thorough as well.
If you still want to troubleshoot Hexo, try looking into other people's public repo's.
If you want to try Hugo, it's even quicker,
www.gohugo.io - there are videos, it takes literally minute to set up.
best
Roy