I always buy the top-of-the-line paint. Sears is OK as well as SW, but get their best product. Just my opinion FWIW
I personally really like the "Medici Ivory" shade for a living room or dining room at SW.
Typically, use semi-gloss on all walls & the ceilings can be satin. Most people choose off-white walls with pure white ceilings.
A step you didn't mention is "Prep" You're preparation work before paintint is important. I suggest taking off all wall plates, filling all small nail holes with puddy & sand with flat sanding block. Wipe down walls with cleaner such as TSP to degrease, and let dry. Remember, paint won't stick to grease. Especially clean around wall switches where hands smear grease and the stairs railing. Ceilings typically don't get as greasy except for kitchen and bathrooms. Just some advice/thoughts. I'll quit rambling now...