Agreed: get a gauge ASAP. Most people underestimate how helpful instant & resettable trip MPG feedback will be.
It's equivalent to lap times or drag times -- you want & need the instant feedback to be able to up your game. (Which is why some call them "game gauges".)
I assume the car is hobbled somewhat by low gearing, if it's like other sport model Hondas. But having the stick will go a long way to letting you get the most MPG from it for sure.
You can search the garage to see what else is in there...
EcoModder Fleet list - EcoModder.com
And welcome to the site!