Just ask for a spot when you see someone available.

You humble yourself, you grow as a person by practicing communication, and you get to try to lift a little heavier as you know someone is there to help you when you eventually fail a rep (which is important if you're trying to bulk or get stronger). You thank them after and maybe even give/get a fist bump. That's it. Do this often while being mindful of people and their own workouts. One day, someone will ask YOU for a spot. Oblige.

Asking for a spot is absolutely a frequent and everyday occurrence at pretty much any gym. Most people are actually pretty honored when they are asked to spot someone's PR attempt.

You don't really have to make a ton of small talk unless both parties are open to it, but you'll get to know the regulars who will eventually talk to you.