One week stay using Brisbane as starting base
 

We will be traveling to Brisbane mid October and had planned to see Brisbane and drive to GBR. After reading numerous posts I'm realizing GBR might not be a good idea on a tight budget and limited stay. Re-evaluating plans now and looking for suggestions as to where to visit-like water, hiking, kangaroos, rainforests, some city and culture.

If you are young head south to the Gold Coast. There is lots to do there besides the regular tourist things. Head up into Lamington National Park for the amazing birdlife.
Currumbin Wildlife Sanctuary is good for seeing the native animals and Sea World is worth a visit.
If you are more mature head to the Sunshine Coast. Great beaches at Noosa and inland there are the Glasshouse Mountains National Park. Australia Zoo is close by and the seaside areas of Maroochydore and Mooloolaba.
For some culture and city life Brisbane has the Queensland Performing Arts Centre with many shows and concerts on all the time. I really enjoyed a look at the Brisbane Art Gallery (across the road) on a recent visit. Great food in Brisbane restaurants as well.

If you really want to see the Great Barrier Reef and rainforest, would you be better off changing your flight and fly into Cairns?

As tasmangirl says, the Gold Coast (south of Brisbane) or Sunshine Coast (north) are both great. Gold Coast is more glitzy, more tourists especially from Asia, lots of highrises etc but still some nice beaches etc. We like Burleigh Heads which isn't quite as built up as Surfers. The Sunshine Coast is quieter with lovely scenery, if you have the time you could visit Mooloolaba for beaches and restaurants then drive to Maleny or Montville for the mountain scenery. You'd want to spend a couple of days doing this if you can.

Kay

Agreed with the others. But also at Noosa there is a stunning coastal cliff walk which goes through a rain forest type spot & the weather would be perfect & it's not high season so it won't be too packed with tourists. Also nearby is Mount Coolum. It has a walk to the top & has absolutely breath taking views of the entire area! You could also do a day trip with a tour from Noosa to Fraser Island. You can see Dingoes, go swimming in a beautiful lake, see the rainbow beach etc. It's a really great day but only recommended to go to Fraser Island with a tour because if you don't know the tides and the wildlife you can lose your car to the rising tide!