sensyu wo mukae ni iku mae ni, kitte wo yuubinkyoku de kaeba zikan wo setuyaku dekiru.

Japanese often uses a noun or nominalized verb + に + motion verb (行く/来る) to mean “go/come to do X.” Here, 迎え is the noun “pick-up,” so 迎えに行く literally means “go to pick (someone) up.”
By contrast, 迎える is a standalone verb “to welcome/meet,” usually implying the subject is already at or near the location. 迎えに行く makes it clear you’re going somewhere to pick up the player.

To say “before doing X,” attach 前に directly to the dictionary form of a verb:
 Verb-dictionary form + 前に → “before doing that verb.”
So 行く前に means “before going.”
(If it were a noun, you’d use の前に, e.g. 試合の前に “before the match.”)

ば here marks a conditional “if/when.” The ～えば form of 買う is formed by replacing the final う with えば (買う → 買えば).
買えば means “if you buy…” or “when you buy…,” showing that the main clause (時間を節約できる) follows as a result.

In Japanese, で marks the place where an action happens. Since buying is an action taking place at the post office, we say 郵便局で買う.
By contrast, に after a place usually indicates direction or destination (e.g. 郵便局に行く “go to the post office”).

節約する is “to save” (time, money, etc.). To express ability/possibility (“can save”), we use the potential form:
 for a suru-verb, 節約 + できる → 節約できる.
Thus 時間を節約できる means “you can save time.”

Japanese is fairly flexible with noun order before the verb, so both 切手を郵便局で買えば and 郵便局で切手を買えば are grammatically fine and mean the same thing.
The typical pattern is Subject-Object-Place-Verb, but swapping object/place just shifts emphasis slightly.