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Steal all we know is that they're a very rare drop (rarer than familiars, which staff have mentioned are at a 1% drop rate and below) and they do NOT drop in Mire and Crystal Pools. some people swear by Sandswept Delta and Arena luckwise, but if you're in the just-starting-out phase, neither of the two more "starter"-y venues are going to be very useful to you. there's always a
chance Eliminate will drop there, but odds are you're going to be waiting quite a while.
even just one would help immensely, and make it much easier to get others. if you max Fairgrounds every day for a week, that would give you enough treasure to buy one. if you play Shock Switch and/or Artifracture, depending on your playstyle, it should take you an hour/hour and a half to max the streak. if you have the time available, i honestly recommend doing this over hoping for it to drop.
as for the question of making money in general: since you're new to the Coli (the big moneymaker for most users), Fairgrounds is going to be your best bet. for smaller additions, you can answer Tomo's trivia, sell Baldwin transmutations, trade junk to Crim, and bond with available familiars. once you get a good grasp of the economy here, flipping items and hatchlings is also a valid method of moneymaking. i'll drop guides related to these
here,
here, and
here. there's also the option of doing a creative service such as skin/accent making, drawing, and/or writing and the like.
as a note, i took a look at your lair. i can't tell which ones are a specific Coli team as it looks like most of your adults are in the process of being leveled, but most of them have well-rounded stats. this is
not good for the Coliseum and if they stay that way, they're going to struggle. :/
Culex's guide is good if you take Eliminates into account, but if you don't want to buy them/wait for them to drop, you can follow the
Sedona build instead. assuming you're the one doing the leveling, i would strongly recommend you stop leveling your lair as a whole and instead just focus on three for now, and then level the others once you have a team capable of doing so quickly. it'll save you a lot of time.