Using web services

This question is maybe easy or unnecessary for you but I'm stuck here.

I'm trying to make application which store your spending money information. I finished the interface of the app, but the sql part isn't done because i wanna use that sql from internet. As i know, i should use web services ( maybe there is another way ). It should do like add 5 dollar to marketing, add 20 dollar to fuel categories.

1. Is the best way using web service?

2. How am i going to create and use my own db? ( i mean do i create db on sql server and upload it to host, or creating db with codes on android studio ? )

3. I've looked a lot of web services tutorials, but all of them is very confusing. I need tutorial with very basic explanation. Which tutorial or example do you suggest me?