You don't say where you're staying.
A lot of the best restaurants are in/around the market area such as D'Jannys, Lapa Lapa, Condor, Iris, Far A, Bombay Grill (Indian ) China House ( Chinese ). These are a lot cheaper than places on the main street.
The beach bars/restaurants are dearer than those just one street back.
Away from the beach local lager ( Zagorka or Kaminitza ) can be had for 1 lev a pint ( 50p ) whereas beach bars will probably charge 3 times this ( still lot cheaper than home ). Local spirits such as Flirt, Savoy are approx 3 lev ( with mixer ) but any imported beers/spirits will cost about same as home. The local stuff is excellent by the way.
Cocktails are usually BOGOF at around 6-8 lev. If you want unwatered, true strength drinks then go to the Condor Bar which is next to the restaurant on the main road just past Club Mania & Post Office.
Bulgaria is the cheapest destination in Europe for food/drink, portions are large and big measures.

On the strip a number of bars have live bands such as the Funny Pub. Great band called step By Step.

you wont need loads of money, its so cheap in SB. Julie's is lovely for a good steak, Toonman has given you a good selection of good eateries but once your there I'm sure you will discover loads more.
Have a fab time in SB