Its been a few years since I've built one. It can be very relaxing. Put some good music on, or a show, and just model away. There are a few things to note before getting started. With Gundams, there are different grades, and those grades reference build quality, and level of skill.
High grade - standard build. Easy to put together, but models don't look as nice, and aren't able to be posed as much.
Master grade - usually bigger size. armor is built on top of a skeleton frame usually. Harder to build, but they look better and allow for more poses, and what not.
Real grade - Newest build type for gundams (only a few years old actually ) Basically these are the build type of a MG, but the size of a HG
Perfect grade - The end all be all. Usually these models cost hundreds of dollars, and can be massive in size. I have yet to build one. Def don't start with this one.
(deeper explanation of the grades.
Gundam Kits Australia)
You also wanna get yourself a good pair of nipper to remove the pieces from the plastic runners. Panel line markers are also a quick way to make your model "pop"