How long have you possessed the bike? I sounds as if something has grounded thus draining the battery. Hook up an ammeter at one battery pole then the other and note any drain.

 

Easy test is to disconnect the negative terminal with key off, and hold it away for a minute, then touch it back gently to the battery post and see if there is much of a spark. A very tiny one would be OK if you have a clock, radio, GPS, computer memory ,etc. The charging system needs to work too.
Here is an easy test of the whole system.

Put your meter across the battery and see if at rest it is at least 12.5 volts. May need a charge first.
Then watch it while you crank it for 10 seconds and it should be above 9.5 to 10 volts.
Then while running see if it can stay up to 13.5 to 14.5 volts as you rev it above 3000 RPM.
That will tell the basic health of the battery and charging system.

 

It's possible that you got a bad battery. Happened to me several years ago.

 

Brand and model number of battery?

 

After 7 or 8 tries, the battery can barely keep the lights on.

You should expect that. 7 or 8 tries is a whole lot of drain on a battery. The real question is: Why doesn't the bike start sooner?

@swifty2014 outlined what should probably be your first tests. If your battery does need a charge first -- and you don't have a charger -- then put a load test of the battery ahead of that. Many (most?) auto parts stores will do a load test for free AND charge up the battery first if it is low. The load test will tell you everything you need to know about the battery -- and is basically what you'd be doing while watching the voltage drop while cranking the starter.

Rectifier?

Unlikely. Same for the stator. Being able to crank the starter 7 or 8 times indicates that the battery IS holding a charge.

Ignition?

Or fuel? One or the other seems more likely.

The problem is that the bike won't start. Make sure the battery is good (to turn the engine fast enough) through a load test -- at a parts store or as swifty2014 explained -- and, if so, move on to issues that would keep the bike from starting. Better doing that with jumper cables connected to a car battery because it will have far greater cranking power.

One relevant question: How long has the bike been sitting since last run? If it's been long enough for all the fuel to evaporate from the carburetors then you have the answer right there. You'd need to fill the carbs by cranking the engine; that should be done with an auxiliary (i.e. car) battery attached to avoid draining the motorcycle battery too low.