Imo the most important amps/merges are Rafoie, Rabarta, Gifoie, Resta and Gizonde because they're the most spammed when nuking. Red/Blue/Yellow merges are decent to have before you find the other merges though. Here's my take on the merges: Foie: Don't really need a merge for this. Wastes inventory space, Summit Moon is good enough Gifoie: Good for lizards/Merissa A's and Canabins, stopping zu's and dorphons and etc Rafoie: Blow shit up, good merge Red: Can still make good use out of slightly stronger Gifoie+Rafoie which are commonly used techs Barta: Summit Moon is good enough Gibarta: wtf Rabarta: Freeze shit, good merge Blue: Might as well try to get Rabarta merge for more damage Zonde: Summit Moon is good enough Gizonde: Common use before was for PoD on Shambertin but now PoD is dead. Still a good spell cos high damage and fast cast for stunlocking certain enemies Razonde: 3 Seals is a better alternative Yellow: Can still make good use out of slightly stronger Gizonde+Razonde which are commonly used techs Resta: Great merge for support if you're male FO Shifta/Deband: Striker of Chao is easier to get and boosts both S/D range Anti: wtf YinYang: jk
Edit: Forgot to say the price, but Yellow Merge I think is 5pds, so I guess you can expect 1~2 pds?