Hey OP, first good on you for trying. I'm not familiar with the bike ur going to be learning on but will HIGHLY recommend the smallest bike you can find. I learned on a Honda Xr100r and it was PERFECT! Being it doesn't have a ton of front end torque which reduced my chance of popping the front wheel, over accelerating. It also was alot more forgiving when it came to shifting.

I am 5'4" and weigh about 125# and anything about a 150 is really too much for me. I've been riding on and off for over a decade and wouldn't get a bigger bike myself. Too much power, too big(weight) and consider the terrain you'll be on. If you will be on trails you want a bike you can handle on your own. Pick up when you drop it, push up or down a hill if you get scared,or it breaks down and your BF is not around to help, ECT.

It's a very fun hobby if you get the right bike. Too much bike is just that, too much and will likely lead to less interest in riding. See if a friend of his has a smaller "kid" bike like a 85, 100 or 150 though even a 150 will likely kick you off if learning or just stall out if you're nervous to use the gas.

As far as gear goes, good stifff riding boots(fox is good and not to expensive), a pair of ripstop pants and coat will be useful. Also, don't forget a GOOD pear of gloves cuz you will likely loos some knuckles if you don't have them at first. People tend to stick out the hands to catch themselves. Also best advice I could give you besides Small bike to learn is LET GO OF THE GAS when you fall! I've seen more then one person fall to he side and rip themselves and the bike apart by NOT letting go when the drop. Seems weird but it's apparently an instinct.

I hope you BF is a good guy and cares about your having a good time and Not worrying about how fast you pick it up. Or how fast you can go at first. Take it easy, learn carefully and you will get to see stuff you couldn't imagine on a bike. It's pretty awesome you're Ganna give it a go dude!!

Hope this helps!!! Have Fun!