Malboro and Ruby Dragon auto-spawns
Sorry, if this common knowledge in the FF8 community, but you can make these two (and maybe others) with almost 100% certainty. The Malboros before the Lunar Cry on Great Plains of Esthar, and the Ruby in that forest near Edea's house.
Just 'Save' your game in these locations. Then hard-reset your console if you're playing OG FF8, or go the the menu and 'Exit' on the Remaster. Then load the save and voila... enjoy your spawns. Got lots of Fury Fragments and Enery Crystals and then later Malboro tentacles in a VERY short amount of time this way.
(For Malboro encounter: One char with Pain, Sleep, Confuse, Berserk junctioned to Status-Defence x4 (from the Shumi Village side quest). Then Esuna and use Berserk spell on Squall (with El-Att 'Fire'). Or Quistis' Degenerator I guess.