Hi, for first time starting off you’ve done pretty well. You got the posing done pretty well and it doesn’t look awkward, the lighting is also pretty good as it keeps the chracther into question. I would suggest you to add a background and maybe a text and it’ll be perfect. Keep improve
There are many rigs you can find online for different body types. I would go searching using Google to find one that works for you. Some list them on online storefronts of sorts, but they are usually free.
I like how it is at the moment. I would do a couple of small things to hopefully improve it even more, these being changing the facial expression, and perhaps adding more ambient light (a soft HDRI, or other less intense lights behind / around the character) to dampen how intense the main light is. Having only one light and having to compensate for that by increasing its brightness tends to make the overall lighting harsher, which is why it can be a great idea to add some extra lighting.