FOSS gamedev and creative worlds

I really want to play this game, but it laggs me crazy !!! Any tips on how to reduce it?

Do you play singleplayer or on a server? Try a server first. That saves your machine from having to run the server as well and may help if it's very low-end. If it's a framerate-related problem or not high-end-graphics-hardware (i.e. in a laptop), disable shaders. Try a server not too far from you to reduce real lag. If it's just taking endless on the initial connection to a server - then live with it (once!), get a can of coffee and a cake, and after a couple of minutes you're done and have your cache filled. The next connection to that same server will be much faster.

For further help, you'd have to provide more information.

Besides Sokomine's solutions these things might help:
- updating your graphic drivers
- getting a better or different graphic card (or playing on a desktop instead of a laptop)