The Vac is good, just don't go to a motorcycle shop and pay $75 for it. Go to Autozone.
Some air in the system will not cause break failure like you describe. You can still have a good amount of air in the system and still get enough preassure to engage the break.
I have a changed a crap load of brakes in cars and on my bikes many times. Many things could be the problem, MC, calipers, discs, breaks, pistons, etc. You are just going to have bleed the system entirely and troubleshoot.
First, Do everything AA told you.
Then, check for leaks around the system, at the MC, calipers, hoses.
If you don't see any visible issues with your system then proceed to bleed.
Bleed the system with a vac or you can just use a hose. You can buy them at autozone. I actually like using syringes for my brake work. I will explain later.
Before you bleed secure the resovior, remove the cap, fit your hoses, lossen the bleed nut, and slowly bleed the system while making sure you add break fluid to the res. Depending on your system you may have more than one bleed nut. Do this on all bleed nuts even if you want a total bleed, it helps purge the system of moisture. Keep bleeding the system until most of the bubbles in the hose are gone.
Note: this can take a while, so have enough fluid handy. YOU WILL NOT BE ABLE TO REMOVE ALL THE BUBBLES, only time will help. remember bubbles will eventually float up to the resovior if we do it right.
Tighten the bleed nut when you are finished. Test your brakes, look at the calipers and make sure that there is movement. If you have a stand put the bike in neutral, spin the wheel, and make sure your brakes bite.
Now, an alternate method which I use is to completely bleed the system dry and then add fluid through the bleed nut with a large syringe. This method usually saves me about 45 minutes. Most of the bubbles are pushed up with the force of the brake fluid.
If you are getting bite, enough to stop the wheel, then use a tie wrap to engage the pedal overnight whle keeping you bike on the stand. This will help float more bubbles towards the res.
If you are still not getting the wheel to stop then you have some other problems which you could look at yourself or take to mechanic. Most motorcycle repair shops can perform brake work on your bike. They have the time and tools to troubleshoot the problem. You can always purchase the parts from your local triumph shop and have another shop perform the labor.
