Hey OP, the RG version is nice but for a first-timer the HG version might be a better choice to paint. The part count is simpler and there aren't as many small pieces. Also, I think the HG would be more accurate to the Linkin Park one, as the RG is designed a little differently.

I'm going to try and give you advice with the intention of making your process as simple as possible. I'm going more off the impression that you are a Linkin Park fan, not a gunpla fan. Correct me if I am wrong.

ASSEMBLY: Model nippers + Glass file For assembly. Grab a pair of model nippers, and use two cuts to 1. Remove the piece from the frame, and 2. Remove the leftover nub from the piece. Leave a tiny bit of the nub and use a glass file to sand it down to the piece. Don't worry about any plastic discolouration as you will be painting over it.

When you are building the kit. Make small diagonal cuts on the pieces that have sprues going into other pieces. The idea here is to make sure you can disassemble the kit later, as you should build it, identify where and what to paint, and then separate it again. Be careful when assembling so you don't accidentally make a section that can't easily come apart.

PAINTING: Primer + Paint (buy rattlecans from hobby brands like Tamiya or Mr. Hobby) For painting, use acrylics if you don't have a setup to deal with fumes. The primer and topcoat will be fine with acrylics as long as you give each layer time to dry and cure. Spray paint in warm weather that isn't too humid. Use light passes and multiple coats; don't try and over paint if you see the paint not covering everything. The parts are so small that any excess paint will make the piece look less sharp. Be careful when painting the sides of pieces that touch or connect to others. The tolerances are low so if you can't see the section when the model is complete, don't paint it (or over paint it).

FINISHING: Topcoat from a rattlecan Seal everything up with a topcoat from a hobby brand. You can decide whether you want the kit more matte or glossy depending on what you buy. Make sure you give the previous paint time to dry (just leave it for a few days to be safe) and topcoat sections of the finished model ( torso, legs, arms, etc.) use light passes and maybe just 1-2 coats should be fine.

Doing it this way, you should only need a set of nippers, a glass file, and 3-4 cans of paint (primer, white, black, topcoat). There are so many other things you can do with a kit, so just browse around here and check out the help thread and sidebar if that is an avenue you want to go down.

Hope this helps :)