Gunpla modeling is certainly easier today than it's ever been, and all you actually need to get started is a basic High Grade kit (here's my recommendation for beginners) and wire side cutters, like the kind that's used for jewelry, to cut out the pieces. 

In the photo, I'm using Tamiya side cutters, which were designed for hobbyists, not jewelers. They're stronger for when I'm cutting through even big pieces of plastic. 

I use a hobby knife for cutting down the nub that gets inevitably left over after I cut out a piece. 

It's not just that your Gunpla will look better if you use a hobby knife. It's also that the pieces will fit together more smoothly without any extra friction. 

I've found that when I try and apply stickers to Gunpla manually, the oil on my fingers makes the stickers less sticky, so now I apply them with tweezers. 

Tweezers also allow me more precision than when I'm using my big, stubby fingers-I can more easily line up where I need the sticker to go.

you can buy Gundam-brand markers specifically for inking your Gunpla, most frequently during panel lining. The fine tip of the pen is perfect for getting in the ridges of Gunpla parts so you can add lifelike detail and contrast. Read our panel lining 101 tutorial for more on that.

Excepting markers, you can buy all of the tools I already listed in one kit, the Tamiya Basic Tool Set, for much less than it'd cost to buy them individually. This set also comes with some stuff you probably don't need yet, like a metal file for polishing, that will be useful when you want to get more advanced.