The 2.5" fry mold from do it would be at the top of my list to get.

As for the plastic... If you are satisfied with the spike it plastic I'd save the money and get more of it. Putting savings towards another mold. You can always get the other plastic down the road. I don't know what quantity of plastic you buy at a time. I buy in 5 gallon buckets so there's a good bit of savings between the two. Adding molds to the collection would be my goal if I were you.