For a first kit: build it clean, panel line it, decal it, topcoat it — no paint at all. Snap-fit kits are molded in color, so that sequence alone produces a shelf-worthy model while you learn cutting and finishing.
When you start painting: build and prep sub-assemblies (arms, legs, torso separately), sand and prime, paint while parts are still apart, then assemble, line, decal, and seal. Painting a fully-built kit means fighting your own model for access to every surface.
Go deeper in our start here guides.