I would avoid the River Maun as the stretches that run through Mansfield and the immediate surrounding areas are no fishing by order of the local council... you'll probably wonder too as it's very narrow and shallow for most of its length but does hold fish, there's a stretch out at Walesby Scout Camp (around 12 miles away) that's on the Notts AA book but I wouldn't be too cut up about it if you decide to give it a miss.
Field Mill Dam is right in the town centre, directly opposite the football ground... it's a shallow but nice little mill pool that holds perch and a few pike amongst other things and is free to fish. Due to it's location it can get a bit of a tip with litter but fine at the moment as I cleared the place up myself a week or two ago and it still looks ok at the moment.
Kings Mill Reservoir is another... but huge and daunting, directly opposite the hospital and fishable on a day ticket from the bailiff on the bank (if you see them).
And just beyond that you have Sutton Lawn, a park lake which holds most things including some big pike, again day ticket on the bank (I think?).
If you can live without the spinning buy a pint of maggots and give Berry Hill Park a try. It's a nice, small park pond with a couple of islands set in lawned grounds on the edge of a small wood with car park overlooking a few hundred yards away, day ticket on the bank and barely any deeper than the length of the rod handle but you'll bag up on roach, tench (even now) and some occasional chub and carp... expect the odd big goldfish and fantail too that's outgrown its bowl.
Good luck with it, hope you enjoy your visit
Edited to add: Almost forgot... Vicar Water at Clipstone (3 - 4 miles) is a lovely water set in a country park, day tickets on the bank and lots of perch (not sure about pike or whether spinning is allowed) and well worth a visit if only for a walk.