Even if you max out every item available in the shop, you'll still start out with a maximum of two BUDDYs. I guess that's part of the game's balance. After all, you'll end up dominating the game pretty quickly anyway.
It was a bit disappointing that when I chose a diver as my starting BUDDY, I got two divers, but when I chose VOLT THE EEL, I started with just one diver and one VOLT THE EEL. I really wanted to try playing while surrounded by four VOLT THE EELs.
With four such powerful BUDDYs by your side, you can dive into shark-infested waters with peace of mind. I had a lot of fun. 🙂