Do you want to make a cool and powerful multisphere file? Here's how, in a set of easy steps:
Buy a box or gold box of Set 10. Hopefully this gets you one copy of each of the following cards: Mediator of Sun and Moon, Folrart Flame Swordsman, Wandering Bard, Crest Saboteur Knight, Exiled Military Aide, and Mermaid Observer. These cards will henceforth be referred to as Moxies (short for mini-proxies). Go to step 2.
If you want to make a level 3 rush, go to step 3. If you want to make a mids file (not recommended for newer players) skip to step 6.
Pick your favorite two spheres and build a file that uses both of them. Put ONE COPY of the appropriate moxy in it. Go to the Single Player Arena and step 4.
Fight every bot in the Single Player Arena. Start each game by raising your two favorite spheres to level 2 and playing your Moxy. Adjust your file as necessary if you can't beat a bot. Once you've found a version of the file that defeats every bot and is fun to play, go to step 5.
Go to Folrart Arena and use your file. Good luck! If you get bored and want to make a new file, go to step 2.
Pick your favorite Proxy and use point cards to get one copy. Make a file that uses that Proxy's colors, and throw in a moxy with the appropriate colors as well. Go to step 7.
Go to the Single Player Arena and fight every bot. Start each game by Skipping, then playing your proxy, then playing your moxy. Tweak your file as necessary. Once you have a file that beats every bot, go to step 5.
If you somehow break this infinite loop, I would love to get feedback and suggestions for this guide. Sorry if it's terse, I don't mean to be. I hope this helps people who want to play multisphere!