Re: Building my bag.
I think wedge is a good suggestion. I'd suggest less than the 60 though. I went with a 56 sand wedge which has both helped enormously when I wind up in the sand, and is IMO a bit more generally useful than the 60. My only problem with my choice is that the wedge bounce that's good for the sand is not ideal for some of the hard lies I get around here when it's dry. I'd think that adding the 52 with a lower bounce would be the next thing to do, but clearly others disagree.
I was in your shoes not too long ago (still sort of am) so here's a couple words about what I've been doing. Of course, you may want to consider my handicap before taking too much advice...
After that, I'd say take a hard honest look at your game and figure out what you need. When I was in your shoes (10 year old starter set) my decision was more or less made for me when my irons started breaking (hosels snapping off!), so I had to replace them. I think that was a pretty good move, as those and the wedges make up most of your strokes, and certainly the most important strokes. I was at a bit of an impasse as to where to go next. My putter was ok, so I didn't really see that I was leaving many strokes out there that I could pick up there. I'd talked myself out of a driver since I drove well enough, but wound up getting one as a gift a few weeks ago. That turned out to be more helpful than I'd expected,. It's helped me reach the fairway a lot more and with a bit extra distance. A 3W might have been more useful since it'd be helpful on long approaches, but honestly, I don't need to be going for 200 yards off the fairway at my handicap yet, it just gets me into trouble.
Good luck, I had a lot of fun adding "real" clubs to my game, hope you do too!
Oh, by the way, check out callawaygolfpreowned.com if you don't have used stuff nearby. That's where I picked up my irons, and while they don't have the lowest prices, they have good selection (even other than callaway) and my experience was that their ratings are honest and a bit conservative.