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

Always Prime any unpainted surface. If you want more information on the type of primer to buy, tell me what type of wood you have? lol was that a pun 🤪 lol. Good luck with your project.