T3i, 18-55mm, 55-250mm: Will This Package Be Good For Me?

I have a T2i with the two lenses you mentioned, plus a 50mm f1.8 for portrait and low light.  Before that I used a superzoom (canon s3is).

I agree with 10s comments on the super zoom camera.  I think you'll find it limiting.

Most responses have focused on shooting wildlife but you also mentioned a desire to do portrait work.  I believe you'll benefit from having a dslr for that, and a large aperture lens to narrow the depth of field: 50f1.8, 50f1.4, 85f1.8 are all reasonable options.

I don't shoot macro so I have nothing to offer except I read somewhere that the 50f1.8 can be reverse mounted to make a decent macro lens.  I suspect the others can as well.