I'd opt for a good secondhand mountain bike.
Something with a sturdy frame, strong rims & a high spoke count, and which fits you well.
Mountain bikes tend to have quite low gears (since they have tripple gear rings), so make it easier to climb up hills.
You can get by without any suspension, and on entry level bikes it's not always of a particulary high quality anyhow.
Often bike shops sell used bikes, which have been serviced, and do not cost too much.
If that is not a option, you could always try Craiglist & get the bike checked over by a bike shop.
Bike brands to look for include trek, Giant, Specialised etc.
Try to find ones still quite relatively new if possible, anything under 5 years old should be reliable.
But most of all, make sure the bike fits you well.
A uncomfy bike is destined to spend it's life hidden in the back of the shed.
