Trades rarely add to talent unless you're lucky, since it requires a "greater fool" and there's a limited supply.
Trades can address imbalance, for example packing some marginal minor league starters for a solid position prospect could build depth at AA/AAA ball. Moving Franco for a young OF in a package. But the Phillies are a couple years away from those A ball players having real trade value (Irvin's numbers at Lehigh are far more impressive than Parkinson in A ball b/c doing it at a higher level reduces risk for a marginal prospect).
I don't think there's a quick fix out there, I doubt Machado will even look at the Phillies (the money will be there from a half dozen teams), and Harper, while he would help, isn't enough to get them close to contention. The other free agents are just Arrieta types, overpaid with a lot of risk (Corbin will get grossly overpaid for a contract year peak, but his velocity declined, wanna bet on three good years out of him?).
In the end, improvement is almost always internal, you can help out with smart moves and some luck (Victorino, Werth), but in the end you have to develop 4-5 core starters and a couple top pitchers out of your farm system. And to maintain a competitive team, you have to sustain that farm system over time.
