I generally agree with Digglez POV, using a Knightly Kite Shield myself.
Pros:
Fast
Light
Cheap
Surprisingly effective
Good coverage, if you learn to position it right
Cons:
Smaller coverage
Low durability, learn to manually block
OFC I use this as a hoplite, mainly to approach archers, and switch to 2H for melee fighting. YMMV as 1H, generally though, you're not going to get much use at all out of a shield with only 4 skill. You will want more points to increase your coverage (helps a lot in melee) speed, resistance, etc. if you plan on actually taking hits - with just 4 shield, some of the PS kings with axes will one-shot your shield.
Note, you don't necessarily need a more EXPENSIVE shield, but more points will make lower skill shields more effective as well.
I'd recommend figuring out how you want to play, and build around that. Shield with a crossbow seems kind of pointless to me to be perfectly honest, you may as well go 2H if you're primarily melee, or drop the shield in favor of more bolts if ranged.