Some good and bad info already on here. I've competed in all 3, my wife has done only multi-ply. I train with a well-known team that knows geared lifting..... so please don't feel like I'm talking out of my rear.
In a nut shell - it's different for everyone.
It depends on form, your build, but most importantly your mind. Geared lifting is a very mental game. The gear doesn't magically add weight to your lifts. It helps but it's still you under that bar.
I've seen 500 pound raw squatters get in to a well broken in suit and briefs and not be able to handle the pressure, eventually giving up before ever going over 600.
I've also seen women like my wife, ( granted, we only train multi-ply. Our raw work is just for accessory and not a great indicator of our strength) - she squats somewhere over 200 raw but is a badass about form and can handle a lot of pressure. She's gone 505 in multi ply gear. She started in an old Frantz poly suit but within a year was in a full canvas with some crazy briefs. Her coming up right in to multi ply under the guidance of a good team helped her become a technician in gear.
Or, take a top tier teammate of mine. He squats close to 900 raw but doesn't like the pressure of tight gear so he's still in the mid-1100s.
Another teammate can bench 575+ raw, but can't handle tight bench shirts. Even multi ply he can't get over the mid-700s so he just competes in a single ply shirt and stays in the 6's and low 7s.
Another guy I train with is around 575-600 raw but is putting up ~900 single ply, more in multi.
It all depends on the individual.
The best thing you can do is to pick how you want to compete and commit to it until you learn the technique. Go find a team that knows whatever gear you choose and listen to them.
As far as ordering gear, the best thing you can do is to start by asking your teammates about old gear, after that look on the net for used gear. Used gear will be way easier for a beginner to learn.
If you do want to go with new gear you have lots of different options.
Overkill is custom made, so it takes a while to get but is the best you can buy.
If you want Inzer NEVER order direct, they take longer than Overkill even for stock stuff.... go through house of pain instead.
Same with Titan, always go with Ken Anderson. He's cool as shit, titan direct has crap service.
For MEtal go through EliteFTS
Good luck.
