How to make my 2001 Honda Civic LX more gas reliable?

I'm not the type to spend money on speed upgrades. I would like to range somewhere between 36 to 40 city/Highway but if there is a way to get more, I'd like to know. What parts can I buy and what can I do to make my car get the best of gas mileages?

Read more: How to make my 2001 Honda Civic LX more gas reliable?