When you first start, ask Koris to help you with the capturing skills. When you are done, you will have a free Apratron but it must be purified. It has a Water Element base, a special attack and also has a magic spell Water Element.
This is being passed on from DarkOmicron from YouTube, but I have verified that it works.
Here's how to get many Arpatron before you truly start your journey:
1) Initiate "Capture" when you first meet Koris in the Beetle Forest.
2) Weaken and capture the Arpatron you encounter.
3) Exit the forest and save at the Barrier Gates. Reload your save file then re-enter the Beetle Forest.
4) Press X in front of where Koris would be standing to initiate his tutorial menu as if it had never happened. Repeat to get many Arpatron for your journey.
Hold X and O while simultaneously pressing the 4 bumper buttons R1,R2,L1,L2.