Advice for first-time campers on sleeping comfortably without spending too much

[Sweetdreamsbeautifulnightmare]

We are first time campers and looking to sleep comfortably .. I mean aren't we all! Took blow up mattresses last week and we’re not comfy at all! Don’t want to spend loads but what is the cheapest way to be comfy?! Self inflating ones seem to expensive! Is there a topper for blow up mattresses?! HELP!

And yes, I have a proper sheet pillow duvet set up. Just back from the Lakes where I slept like a baby.