Vileplume

Dragonite's in gyms? To be honest with ya... Nope

Maybe if that is all you had or you were just looking for something different for the sake of being different. However, Acid/Moonblast would likely be better against Dragonite than Razor Leaf/Moonblast. Grass is double resisted by dragon/flying while poison is neutral.

for gyms, anything goes. When weather is partly cloudy I'm using rock blast golems as generalists.
for raids, If there are enough people still anything goes, crowded raids mostly yield +1 damage ball regardless of counters

Nope. Razor Leaf has poor energy gain and is double resisted by Dragonite, Moonblast is only single effective, is a low damage move for 100 energy, doesn't have STAB and Vileplume's attack is mediocre.

Not that gyms are difficult but using a Vileplume for Dragonites is just wasting your time.

Fairy typing is good defensively against Dragon moves but several pseudo legendary Dragons have double weakness e.g. Garchomp, Rayquaza, Salamance and Dragonite have double weakness to ice.

1) Vileplume isn't very good. It's decent but not good, stat-wise

2) Its quick move at best would be neutral STAB against Dragons

3) Most Dragons carry flying moves or fire moves which are effective against Vileplume

4) Vileplume probably won't survive against a high-attack Dragon long enough to use a one-bar move given that its best EPS move, Acid, is only 10EPS

5) Moonblast is a relatively poor Charged Move

6) Dragons are best countered by Ice-types, whom they are often double-weak to, or by Fairy types, whom carry double resistances to Dragon moves. Vileplume's Charged Move is Fairy but not its type, which is a valuable distinction.

If you have a fast TM to spare (most of us probably do), and have no other relevant pokemon to use it on, I will fast TM it and use it as part of a rayquaza sacrifice team, transferring it later. It will do a decent job as far as a sacrificial mon is concerned, provided the moonblast hits.