I just did a couple of weeks in BC and camped for most of it.
I would think $100 a day would be easy to do.
Maybe even approaching luxury.
Provincial campgrounds run around $12-20 a night. Depends upon if you buy wood or not. There are lots of crown lands that you could camp on for free but it is hard to tell what is crown and what is private sometimes. I stayed in one private campground that was only $20 and included shower and laundry!
If you camp in the National Parks you have to pay a daily parks pass in addition to camping fee and fire permit (wood). A yearly National Parks pass can be purchased if you plan on doing a lot of National Parks.See link
Campgrounds in Banff/Jasper tend to be full. (Not so much after September long weekend) They can be reserved ahead though if you know when you will be there. You can book online
Hint: try to start your day early and look for camping by about 3:30 PM before the evening rush for campsites starts.
I got a Primus OmniFuel stove
and loved it. It packs up tiny and boils water in about 3.5 min. There are lots of other versions are available but I plan on using this little beauty a lot.
I don't eat much for breakfast but tea, cereal, granola bar. A couple of bucks.
I usually ate either lunch or supper at a restaurant. $20 +/-
Supper at camp was usually some variation of MRE/one pot style supplemented with bread etc. I shopped at grocery stores along the way. $5-$10. I quite liked the boil in a bag variations from Asia House. If you like Indian curries they are not bad.
Gas prices vary but you can go a long way on a $15 fill on a Wee. (less on a Vee:rolleyes
Gas was available within driving range anywhere throughout Alberta/BC.
Right now campgrounds in some parts of Southern Alberta are closed due to extreme fire hazard. That can change quickly with a bit of rain though. Not sure about current BC fire hazard. Some of the BC forum members should know.