Since I'm doing this on my phone, not on the computer, I rely solely from apps from the AppStore. These are apps I use and you will probably not understand my tutorials if you don't have them, but something similar to it will be just fine.
SuperImpose: A must have out of all the apps. Before using this, I had at least 9 different editing apps. It blends nicely, great for editing, great erasers, et cetera. But the best apps have to cost money. No worries, only 1.99 USD. (Another choice is to use a Cracked App to get it)
Pixlr: It has a ton of effects and filters, on the plus side it is free. It is great for covering up flaws and adding that final touch, also having many colored filters.
Picsart: Can also be a substitute for Superimpose. Has a lot of filters and, unlike superimpose, it's free!
Phonto: I use this for adding text and whatnot. It already has a lot of default fonts, but you can download more from free font sites.
Basically ever app I use. C: An improvement from 9.
Edit:
There's a new editor called Superimpose X! It costs about $6 but you can probably download it from a cracked app. You can now put layers and it's almost like photoshop