This isn't advice, but I also have a MacBook Air, and you're correct. The trackpad isn't very efficient. I'll be looking in the comments for recommendations :)

I use my laptop and a drawing tablet or plug in mouse and haven't had much issue.

Also, definitely go to the adobe website and log in with your student email. Your school may offer it for free like mine does xD

You can get a decent drawing tablet on Amazon for like $50. Totally worth it!

I have just downloaded it and unfortunately it seems my university cut costs and didn't include photoshop in the package

Yeah I've considered a cheaper tablet but I feel they won't withstand over time. Luckily I work for a telecommunications company so I get good discounts just don't want to tie myself into another contract

Maybe I'll just try and mouse first and see how I get along!

Try ebay I got my bamboo tablet off there in excellent condition for £11, because the people selling it literally didn't know what it was lol xD

Might just get a small bargain on there.

I use a pc, but recently got an Ipad and pencil. I had to get an app to let me connect the ipad to the computer, but I found i really loved using the pencil with photoshop. Im not that great at manips yet, but it was fun to use it.