To get your first easy onyx. you can camp tz-haar monsters and sell their drops for tokkul.
When you drop an item, it stays on the ground for 3 minutes, you can use this to do stuff at the bank with a much larger inventory space, just don't forget to pick up your items!
The magic spell Vengeance other, can be used on your UIM if you don't have the runes/magic level
Crystal keys are love, I spend so much of the money on my main on votebooks for my UIM. get them from slayer and vote shop
Collecting coins is still a good thing, you can either buy back untradables, put it in the well or die in wildy to a reg account to transfer.
Be sure to have an awesome first slayer task, under I think 40 slayer the cancel is free.
You can use bonds and votebooks on UIM from a regular account.
Elite Void is probably the best thing to get armour wise in the early UIM game, as you have all 3 styles with just a helmet switch, and they can be bought back fast.
Elite void takes a bit longer to obtain, and is also more expensive to get back from the lost item manager, but the prayer bonus helps so much.
Skeletal wyverns drop most of the supplies you need for early game zulrah.
Farming is super helpful, anti-fire potions and prayer restores are a blessing.
You can use Votebooks and Bonds from your main on your UIM to give them vote points or donor.
As an UIM your inventory space is key, If you are planning to fish like 3k sharks or something, be prepared to have sharks in you inventory for a long time. This is for everything, holding on to skilling supplies just slows skilling down.
The Scorpia Boss, vet'ion Boss, Venenatis Boss, (all in wildy) drop the Rune Pouch at 0.49% !!!
If you're just making a fresh Uim account, I recommend doing all the noncombat skills you can, because once you start combat... bye bye inventory space. - suggested by Kappa
Save yourself a bunch of hours and get all your wilderness skills done while you have nothing to risk. such as agility, hunter, smithing, etc.
Mine gold and make into amulets for 99 craft, this will take care of Mining and most of smithing (finish with ckeys or just do some smithing while you are at resource area). - suggested by Hex
Someone also told me wildy agi course is faster than seers so do that too till 90 while you are risking nothing. - suggested by Hex
Wouldnt bother fishing there, its nice to be able to actually use your food for slayer or something instead of dying to some bored max gear kid with no one to pk. - suggested by Hex