Is there a standardized strength test for gym newbies?

You ask about “gym newbies,” so you must have just joined, or are about to join, a health club?

You shouldn’t need to hire a trainer. I’ve never been to a club that doesn’t offer a complimentary session to each new member – assess a baseline fitness level, discuss goals, and set a personal workout program.

Doing this myself. The gym we joined offers a bunch of free sessions specifically for this. Most reputable ones do

My metric is 10 reps. If you can do more than 10, add weight. If you can’t do 10, reduce weight. Remember, everyone has to start somewhere and it is usually low.

Three sets of 8 are what is most quoted to me. You go to just the point of exhaustion at 8 reps.