You are paying for lightweight and durability when you send more money. That isn't to say that less expensive equipment can't be good. You really have to understand your actual needs. Most people don't really need the lightest, most expensive thinga'mabob on the planet to have a great time. Academy offers some decent stuff but make sure that whatever you buy from them has a reputation for durability. If you aren't going to camp more than 3-4 times a year, then rent the equipment from REI or Whole Earth Provision Company. Personally, I'm not comfortable renting a sleeping bag but that's just me.
If you're on a budget and need to cut corners, then spend less on the tent and more on the sleeping bag. The last time I looked, there were some incredible deals on VERY good used tents on craigslist.
REI can provide some very nice bags but mail order may get a better price. Personally, buying from a local vendor has some obvious advantages if you need to return or warranty the bag or if it doesn't fit or keep you as warm as advertised. Don't forget the cost of the ground pad. You will want a good one. I don't care for the true "mummy" style bags because I don't like my legs and feet so restrained. Big Agnes makes really great semi-mummy bags that are roomy but they usually require a ground pad because the fill doesn't go all the way around the bag. REI sells Big Agnes and they've been around a long time. Good reputation but their temperature ratings can fall a bit short on what they claim.