First decide whether you want paint or stain. Paint is less labor and usually faster. Make sure you prime all the wood with a good all purpose latex primer. If there are any knots make sure you use a specific product for them. Shellac based Kilz is very good for that. If you want dark , purchase a good interior latex. Avoid Behr from HDepot it is junk. Then consider what sheen you want. If you are doing doors use a semi gloss.You can use the same sheen on the crown but remember it will be glossy.Two coats of finish after the primer will do. Make sure you paint all the moulding first ,then install and touch it up.

Use a dark walnut stain, Gliden brand.

I'm redecorating my office and I plan to add crown molding to the walls and painting the doors the same color, I however need advice/help on what color and what brand paint, I don't want to stray away from the dark browns or blacks they're preferable.

p.s on a budget