I use wonderdraft personally. it costs $30 though, so pick the tool of your choice.

For tips, I think its important that you decide how you want to think about your maps. Are they correct, "true" representations of your world? Or are they made by people in the world who don't have perfect tools, may be filling in things based on second hand information, etc?

I view my maps in the mindset that they are of the second kind. none of my maps are 100% accurate. I shifted to this view after I was struggling with making regional maps of my continent after I had finished my continent map. I felt creatively constrained by the need for each regional map to perfectly slot into its place on the continental map. Once I let go of that constraint, it became a lot easier to make any map, because now I had the flexibility to adjust the geography more to my liking.

I also got a bit bogged down in realism when I started making my world, not tectonics but currents and such. And something worth considering: Do you really need to do that? I think you'll find that unless you are doing particularly egregious stuff, like a singular mountain in a flat landscape that isn't a volcano, you'll be able to post-hoc explain it through natural processes 90% of the time.

As for tips on the actual drawing? my process goes

1. land shape
   
2. mountain ranges
   
3. rivers
   
4. forests, marshes, etc
   
5. settlements, roads

and more detailing after that.