Number one rule when creating your model portfolio, do it with a GOOD photographer. Not an amateur one.
If you are doing your portfolio through an agency, as in if you approached them and they said you need to start a portfolio, they should recommend you a photographer and there should be no money involved. If they so much as mention you paying them for setting you up with a photographer, its a scam. Why? Because if an agency is asking you to start a portfolio, they see potential in you and would probably like to sign you. But for that to happen, you need to have some pictures first, so they will contact a photographer and have you swap details, meet up and take the photographs. During the shoot, most often, the agency or the photographer would have contacted a stylist and/or a MUA (make up artist).
If you are doing your portfolio by yourself, as in you want to start it before approaching any agencies, please, for the love of god, do not go and do one of those cheesy as photo shoots in studio with colorful backgrounds and stupid props. That doesn't look good, nor does it make you look good and it also makes you seem unprofessional. To get your portfolio started, do some research online - I find Facebook to be most helpful ahah - and find local photographers. On Facebook, they usually have pages through which they have uploaded their photography portfolios. Inbox them, or email them, and ask them if they would be interested in helping you create a model portfolio. Now, if you are doing this sans agency, it will cost you because you are approaching them and you aren't a professional and nor are they, and you are asking them to do it on their own time.
What should you have in your portfolio? AMAZING shots of you, showing your potential and talent. Most importantly, you MUST have a head shot and a full length body shot. These don't have to be posed, they should look natural. So stand tall, shoulders back, neck elongated, and minimal makeup. For the pictures taken with a photographer, go with a natural look and clothes that fit and emphasize the best part of your body.
These are shots out of my portfolio, the one on the left was a shoot which I did with a photographer which an agency recommended. The one in the middle was a shoot that I organized with a local photographer who was truly fantastic. The last one, on the right, was an organized shoot which a local MUA approached me for a portfolio shoot.
I'm extremely sorry I didn't post anything recently, I just came back from India yesterday, and I'll be uploading my photo diary of my trip soon.
I wish you all the very best in starting your portfolio and your model journey!