Do I need a primer and base coat before using a gloss paint?

Yes , definitely especially raw. A good bonding primer. Depending on type of wood may want to be a stain (tanning) blocking primer (shellac,oil based). If just bond primer warer based Inslx “Stixx” (Benjamin moore store” bonding primer is great!!! 1 or 2 coats of bond primer sand and ready for finish paint.

For a superior finish I would definitely use a primer. For glass like finish: 1) sand raw wood go up to higher grit each time example 120- 150/180- 220 final 2) dampen with water and let wood dry, then sand again by hand with 220 ( water will raise the grain and sanding will make the raw wood very smooth) 3) apply primer - sand with 220 lightly when dry then wipe clean 4) apply two coats of chosen paint *sanding lightly between coats 5) top coat if desired using same sand between coats process