I don't think forms would be a good choice. Forms need to bought for a specific fish with specific measurements. Unless you know this infoyou could bewasting your money on a form. Same with eyes.

I'm not a fish guy, but there are several tools that I would consider necessary for fish mounting.Don't think any of the adhesives or chemicals would be a good choice for a gift either.

Taxidermy.net then to WASCO who has a good selection of fish mounting tools. (Scissors, cheek scrapers, modeling tools, etc.) Also the books and videos mentioned are a goodgift, especially those from the World Taxidermy Shows. If he is really going to get into fish taxidermy a good airbrush is a must. He'll need an air compressor for the airbrush. May buy a fish blank for him to practice painting after he buys paints.