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My first thoughts are how much is the kit your thinking of getting, and how complicated is it?
If it’s costly, I would suggest getting a cheaper kit first to try out, and practice on. Failing that if you have any rwain model making friends ask them for any of their spare sprues to tet out on.
I would recommend a good set of needle files and good quality super glue. Thought to be frank I always use epoxy resin and pin my resin kits. Note also I have never built any Gundam resin kits, only Forge World and Kingsom Death.
You’ll probably want a good supply of the blades for the knife you use.
Be prepared to putty, I use both Milliputt and Greenstuff depending on the work required. So lots of tooth picks, and if possible a multi-purpose sculpting (though not necessary), are useful to have to hand. Plus a small pot of water for lube.
Clean the kit really well before making, as they useually have lots of releasing agent on them..
Some bends in resin kits can be straightened by bathing in very hot water to soften the resin, then holding the part straight whilst it cools
If you have health concerns, where a face mask when filing or papering the resin, so you don’t breath in any of the dust.

Sorry this wasn’t a very well formed response, was kind of stream of conscious thing.

But I hope some of it helps.