help polytunnel Borders

hi,I've just got my first garden and it has a polytunnel on it which I have bought off the guy who has moved off it's about 10ftx24ft  but the inside is just level I was wondering if it would be worth putting raised beds in either side and if so what is the best thing to fill them up with soil or compost or a mixture of both I will be trying to grow sweet peppers in it swell as other things but not quite sure what else yet any help would be appreciated thanks.

I've just got paving slabs down the middle of my polytunnel which is 24x20ish.  2 rows of slabs giving me a nice 3ft wide path.  I didn't bother with raised beds, although sometimes I wish I had as bending is a bit more of an issue with me now.  But I've grown loads of stuff in the border soil, just adding more compost, soil or manure each year.  I usually get lovely tomatoes and chillies.

I have two polytunnels 20ft X 12ft and use raised bed in them both. I have steel sheets 18in high to raise the beds which are 4ft 6in wide. I find them a great asset as they save on bending and also I dont dig them, as such, I simply add manure/compost/leafmould in the autumn and lightly fork it over. I find them very productive and to be honest, I wouldn't be without them. Good luck, whatever you decide.