In case you want a curve of arbitrary genus with arbitrary negative self-intersection, you can do this: Let $C$ be a smooth projective genus $g$ curve on a smooth surface. Suppose $C^2=n$ and take $m$ (pairwise) different points on $C$ and blow them up. The strict transform of $C$ is isomorphic to $C$, so it has genus $g$, and has self-intersection $n-m$. In other words, you can achieve arbitrary combinations of genus and negative-self-intersection. Well, I suppose this might need an infinite field...

In case you want a curve of arbitrary genus with arbitrary negative self-intersection, you can do this: Let $C$ be a smooth projective genus $g$ curve on a smooth surface. Suppose $C^2=n$ and take $m$ (pairwise) different points on $C$ and blow them up. The strict transform of $C$ is isomorphic to $C$, so it has genus $g$, and has self-intersection $n-m$. In other words, you can achieve arbitrary combinations of genus and negative-self-intersection.