tense and universal keys are only needed if you plan to use the antigrav boots. my personal preference is to save the 100 antigrav thingies needed to start that line, because that's an extra 10kg in my pack.
a set of antigrav boots is all that the universal keys are used for, but if you need them for boots, make sure you have enough credits to buy them if you're not going to hunt on larki. as for tense, they are used for many things. the same goes for the boots... make sure you have enough credits. but if you want tense for any of the other things, just ask people who have them (often there are enough in people's storage) to make the item for you. while tense can't be sold at the market, the rest of the items they're used in (other than the antigrav boots) can be sold at market.
but i guess the only other thing you have to worry about is alien whatsitsnames. they go into the first pair of antigrav boots. unfortunately, they can't be bought at the supply tent, nor market. but luckily some can be found by monsters on TA. i've noticed that they don't come as quickly there as on larki though, to you might not have enough for your lvl 42 antigrav boots by lvl 42.
--jason