Welcome to the world of 16 ga guns! They are wonderful when built in a frame size appropriate for the gauge. I have a half dozen or so and use them for a lot of my shooting.
There is a 16 ga "society" online at 16ga.com. There is a forum on that site that includes reload data for all the 16 ga. components that are on the market. A very good resource! I find it easiest to order Ballistic Products stuff ( USA) from Will Bilozir in Alberta. He stocks or can order everything in the Ballistic products catalog. Prices are kinda steep, but it is a specialty market! Be warned that there are no good quality highly reloadable target hulls made for the 16. You can make good loads, but they won't reload as many times as something like the Remington 12 ga STS. I suggest that the single most useful wad for 16 ga target shooting in the Guilandi G/BP16. The cup holds 7/8 oz or so, and it is very useful for light loads in straight walled hulls, which almost all are nowadays. Some wads like the Winchester are a poor fit in straight walled hulls and powder migration is a problem. Fiocchi or Cheddite hulls are also available from Will, and are an easy way to get started. If you are shooting factory loads to get started, Both Federal game load 8's and Remington game load 8's serve as factory target loads in the 16, and the hulls are reasonably reloadable. You should be able to find flats of those shells for about $80.