I began Starting Strength say 2 weeks ago, after a good 6+ months of varying stuff without a lot of knowledge, a lot of machine iso's etc. I had great initial progress and then flat for 4 months, thus the recent change to SS. So yeah get the program right upfront, at least make sure it is compound movements as Dave said.
Too early to tell is SS is any good from my experience, some here hate it, others love it. I think SS (or something like it) at the beginning is probably a safe way to go, thus I am.
I'm doing this variation of it:
Starting Strength Wiki - Wichita Falls Novice Version
I too feel like I should be doing more, but you need rest and recovery time. I will supplement SS after a few weeks with some extra's and assistance work only where time, where I specifically need it most, where it won't negatively affect my next session, and where it means I'm not overtraining. So pretty much the program comes first.
FYI careful on the cardio - I play basketball pretty hard on Monday's, and find that strips back some of the gains I make. Plus you can confuse the body, giving it different stimulus all the time.
And after you sort your program, sort the diet. That was my other failing!