For plastic models, you'll want to check into Tamiya's extra thin cement.
If you ever used spirit-type (thin) liquid glue like Plastic Weld, its the same thing only not as "hot" so its easier to work with. Tamiya Extra Thin was a game-changer for me in the smaller scales.
The good old Exacto knife with #11 blades hasn't been bettered yet.
You'll also need a small hobby file of some kind for cleaning up parts.
Paint starts to get complicated. It depends a lot on where you are, how much room you have to devote to a painting area, how much hassle are you willing to put up with, and in the end- how much better do you want (or need) to get?
I'm not saying your current techniques might be bad. Not everyone has the patience, budget, or time to crank out multi-layer award winning effects. Brush painting is still a viable option, btw.
There are some small tricks you can use to get good results.
For the time being, I'd advise to just get back to the basics at first then build up as you go along.
You may also want to check around your area for modelling clubs.
If it seems like they're more interested in contests and competitions, keep looking. Those kinds of clubs are usually more "cut throat" and you want to find a group that's open and willing to talk and teach how they do things.