Hello, after a long time of clearing rust from the head, rebuilding carbs, and clearing rust from the gas tank, my 07 gs500f won't start. I've gotten it to start 3 times with a healthy amount of starting fluid and having the battery plugged into a charger. I have to hold it over 3000 rpm for it to stay running, but there's a LOT of smoke. At first I thought it was the new exhaust- I knew there would be some smoke but I have no idea how much, and theres also a concerning amount of smoke from the engine, I believe coming from the black cover plate on the engine, but im not 100% sure because it just comes from everywhere. The smoke from the exhaust looks kind of blue in my opinion but I'll have to try to get a video or picture next time I get it started. I'm new to motorcycles, so I'm lost as to what the problem could be, if there is one.

I would get it running and then worry about the smoke (if its blue thats oil and you may need to do a top-end rebuild).
For the bike to run you need spark, compression, fuel, and air

You can get it with starting fluid, so we know there isn't likely a direct problem with the electrics and you do have spark.
The fact that you need starting fluid to start the bike means there is likely a problem with fuel. You say you rebuilt the carbs and cleared rust from the tank but can you go into more detail about what you did and how you know those are not still the issue? I'm guessing something is still wrong with the carbs, fuel lines, petcock, or tank.

The gas tank and lines were full of rust so I used the KBS tank kit and put a fuel filter on. I rebuilt the carbs because the guy I got it from said they needed to be rebuilt and he had a kit. It's very possible I could have rebuilt it wrong. I made sure to drain the carbs and lines of the bad gas, and put new lines on. Also, I put on a new tank petcock

Also something to mention, when not plugged in the starter sounds a lot weaker than when it is plugged in, but I did also put in a new battery

Something must have gone wrong with either the tank cleaning, petcock install or carb rebuild. Since it runs on starter fluid we know there is at least enough compression to run.

Did you fully disassemble the carb and clean all the brass parts and passages of the carb, replace all the o-rings, clean the pilot jets, check the float height, make sure the jetting is stock or close to stock sizes, set the mixture screws to 2.5 turns out, and re-install the airbox w/ air filter? While you are at it you probably want to replace the intake boot o-rings and make sure the boots are still pliable. Even a later model F like your '07 is starting to get old enough that all rubber parts need to be inspected to avoid air leaks.

On a non-running bike with no known history you basically have to reset everything as close to new OEM as possible.

I replaced all the seals, didn't check all of what you listed but I bought a compression tester earlier and
Left cylinder (battery not plugged in) = 40psi
Left with battery plugged in = 65 psi
Right cylinder (battery not plugged in) = <5 psi
Right cylinder with battery plugged in = 15psi

I'll make sure to do all of what  you mentioned while the carbs are out but it looks like I'm rebuilding or replacing the head. I have no idea how it ran with such low compression but why is my compression different between when the battery is plugged in or on its own? Could it be my starter dying or my battery having issues?

How do you test compression without a battery plugged in? Don't you crank it with the starter?

Warm compression specs are like 150+ psi. I think anything below 100 cold compression could be presumed to be totally shot. I presume there may still be some carb trouble but it sounds like the engine's top end needs a total rebuild.

Compression testing is outside my expertise, hopefully someone else chimes in.

I just realized I forgot to do the compression test with the throttle open, will post findings when I get a chance to do it again

Throttle open didn't change anything

The rings are shot. Amazed it will start at all. Bike needs a top end rebuild stat. IMHO.