Sure, I'd be happy to help :)
The main tip I can give for any art is practise. Development takes time, and through lots of drawing you just keep improving. But as for tips that helped me along, here are a few.
Start with a sketch. I didn't do this for ages but it helps a lot. Set the sketch layer to 30% opacity (you control opacity with the slider in the layer editor). Then jus use a normal pencil to do a rough outline of your drawing.
Then when doing lineart on a new layer, quick lines with a slightly thicker brush will be smoother I find, but you can try whatever technique makes smooth lineart for you.
For colouring, my favourite technique is to put in one certain colour exactly with your brush on a layer below. Then in the layer editor press the button next to the layer that just has a squiggly line in it. What this does is make it so that on that layer, you can now only draw on the areas you already coloured in. Perfect for shading! So just shade onto this, and then repeat with other colours.
Also save a lot. I'm not sure if it's just my phone, but sometimes tr app is a little botch and crashes, which fucks up your piece and deletes a few of your moves while doing others.
If you don't get something I've said, or it's not amazing rght away, don't worry, I can only draw like this from over two years experience (I was really shit at the start). So just draw a ton and you'll work out things that work for you
Good luck! n_n