Since you're a beginner and you don't have any clients yet, I think the best you can do is you could take some already implemented application which UX you think could be improved in any way and then find a way to improve it.
It could be not just web or mobile apps, but anything that you think could be improved, like a road sign, or a train ticket vending machine or whatever.
Demonstration of cases like this before-after with a careful and precise description of benefits of your solution would show your approach and the way of thinking and this is exactly what headhunters are looking for.
Apart from that it's a great way to improve yourself.
Godspeed, young one!! ;)