I am a portrait photographer, working on my craft, trying to learn..what will help me level up?
The obvious clickbait options would be a higher megapixel camera, better auto-focus, wider aperture lenses, a questionably heavy tripod, new presets, courses on SkillShare etc etc. While all these answers hold some degree of influence over your skill set, these are solutions to much different problems than learning. These help you take higher quality shots, though the degree of improvement will be easily attributed to the new camera or the wider aperture lens and so on, you get the idea.
As portrait photographers, or enthusiasts even, we are looking at exploring the bounds of our talent and pushing it wider with each shutter click. Most books on photography would say learn to see, heck those are probably the first photography books you'd read "learning to see". And yes, they are correct. They talk about walking around the subject, explore all vertical angles, go deep (macro), go wide, top down, color, expression, leading lines, and so on. What can I offer you ask? Since we already know all this.
A muse. If you are in a boat similar to mine here, years of amateur experience, some shoots, but unable to take that final step to professional quality, and professional gigs; a muse might be the answer. I don't mean here to imply a muse the way some say, take pictures of your friends and family. No, look for a muse that will let you calibrate your skills given a professional baseline of a model's skill. Look for a person that is willing to work with you long term and grow themselves in their talent and portfolio. Explore all your ideas with them over several shoots and truly see what works and what doesn't. Bring out your "learning to see" book now and learn to see your muse in new light every shoot.
As a portrait photographer, you are quite likely to have a bucket list of ideas that you have thought about. Clients are not likely to be great candidates for experiments, maybe it needs getting a bit more comfortable with the models before approaching something as advanced, all scenarios perfectly suited for a muse. One that knows you, knows your style and can easily understand instructions and do exactly what are looking for.
The best part about having a muse and learning with them, is that over time as you go on shooting you are able to add nuance and complexity to your shoots that was impossible previously. Once you have established your style and individual techniques with the muse, it is easy to replicate them with your clients.
