Since you don't want to profit from a "full clubset" buy, you may do it one by one.
The G20s certainly are good clubs - the first with "high" trajectory. Alas, this is least important on the driver. How much longer is it than the Rapture?
Talking about the other woods, one might be enough, e.g. the 3WD. This is because the standard set-up in the higher levels drops the hybrid and utilises a third wedge instead. Dreams of the future for you...
...which might include a further upgrade in the range of lvl 80 (RBZ, G20, R11...).
I suppose that you might play better with better wedges. These lvl14 babes won't compete with the better ones. I propose two short wedges, as expensive as you can handle. Ping, ATV, Cleveland - whatever you like.
Putter: I'd always propose a putter beyond the Spider but since you have it you might as well keep it for a while. The only urgent reason to exchange it would be your outright dissatisfaction with it. And, the choice depends on your putting technique: "ding" or "off-ding".
Balls: Don't know these L1 Callies but I suppose there may be other with better performance. Did you ever try WGT Tour SD, Srixons or lvl33 Callies? Give them a try!