I just did my first practice attempt and got sub three hours. Is this good for a first time speedrunning the game? BTW this was on genocide.

This would place you in last place/second to last so i wouldnt say it was the best time But its good practice for you :)

You can easily sub 2 if you learn the route fuck it, you can easily sub 1:30 even sub 1:20, or sub 1:10 it requires learning the route obviously, which you can do by using the genocide guide thats hyperlinked in the general undertale speedrunning guide.

The full guide that has good introductions to speedrunning, including true resetting, version differences, stuff like that can be found in this link: https://docs.google.com/document/d/e/2PACX-1vSbtlfy6wLQxF_bkZD7hPXZCsnoq1KBPVsmaH3efIbTeBczo8fhZ5PD5Bfgd3w53QtnTG5OSmm1AwMr/pub

The Genocide guide with the route: https://docs.google.com/document/d/e/2PACX-1vS3GWQphBL6LJP8omEMmktJ1xkBfg9yP-8k6uRUmjx5wKXeQ0HNOsN9PA68FCSjVO_Fe4MqFBFq1bDk/pub

Most important thing for sub 2 is deathless, so practice sans and undyne until you can beat them at the very least 1/3, better if you can do it on demand though.

Also, welcome to Undertale speedrunning! I would highly recommend joining the Discord server which is on the sidebar on the left, if you haven't already.