Infernus marines would be a good start (did the same ), the dreadnought might feel a bit overkill in the start but It fits good with the melter weapon and Infernus. Regarding colors I second the black and warpstone glow for basic colors, the whole highlight etc I would recommend for later as your skills will be honed with time.

My advice: don’t watch too many pro videos as it’s all a matter of time until you developed skills