Curtis has a lot of power. He can alter reality. This lets him do just about anything he wants. His powers come from a shard of the Cosmic Cube. His abilities are limited to a 30-foot bubble. Inside the bubble, he can alter reality in just about any way he wants. Objects and effects he creates fade away when they get more than 15 feet away from him quickly. Not instantly but fast. He can create a gun and shoot someone with it before the bullets faded but he'd have to throw something pretty hard for it to not fade too early. His powers are also limited by how much he can focus and concentrate on something. If distracted from an effect, or he stops focusing on it, it'll fade away as well. He can't make anything bigger than his bubble or he'll get it cut off at the limits. He can do more than just make things. He can also change himself and others such as speeding up his healing abilities to supernatural levels to repair his spine after the Abomination injured him. He can do the same to others, giving them things like extra powers or accelerated healing. He's also started learning tricks to get around his fade away limit like creating machines to make objects from materials fed into them. This takes more concentration and can't be done too often as it tires him out. It also doesn't always work right, especially if he tries to do something more complex than he should. He's still learning so it has a chance to blow up in his face.
Here's a page from the comics where he gives a basic understanding of his powers as he's been able to figure them out after about a day with them.