Couple of things.

One post per day. No more, no less.

Instagram stories, dont just add your post to the story, but make dedicated images to be posted to your story, like behind the scenes, how I got this shot etc.

Tag reposter pages and get them to repost your content with credit.

Reels, you have to post reels now. You can still get decent traction on photo posts, but a significant percentage of your posts will have to be video rather than stills.

Persistence. It took me far longer to crack 500 followers than it did to jump from 1k to 2k.

It depends on -

Can you do the 3 shoots all at once?

Whats the travel like?

How many photos, editing expectations and also video expectations?

It sounds like at least an hour of actual shooting and probably at least 1h of travel so is fairly involved.

I would consider also the fact you professor is asking for help and that these are community centres (so may have more limited budgets).

Its very much at your discretion but it may be worth weighing up factors like will your professor give you some industry contacts, more work etc if you help him out.

If you want some actual money talk, at a minimum I would probably charge at least 300usd for this! But I would and have done more charitable style rates in the past for clients (I normally stipulate conditions that they must always credit me for anytime an image or video is used so its not a one way deal, if they pay full price they dont have too).

I would honestly keep the laptop you have and use it.

You would probably need to spend at least 300-500usd to get even a basic laptop thats okay for your usecase. Thats essentially the value of the laptop you already own. Id use it until it breaks and buy another model macbook used thats around the same value.