Apart from the basic C172 and the DC-3, I don't find *any* of the default aircraft in FSX that satisfying. I'd recommend buying
one decent FSX optimised aircraft to start with - one that has all the navigation (and possibly FMS) functionality you need to get to learn the ropes. Military aircraft are fun, but they're pure eye-candy - nothing else.
My favourites are [all the] Captain Sim aircraft - and most of the Wilco/Feelthere range. Some of the Carenado GA aircraft are good, but beware - not all have full ILS/Glideslope functionality.
Keep checking
flightsim deal of the day for bargains - as well as Trademe etc. Occasional sales are usually posted here when found. I picked up most of my Captain Sim aircraft in sales after people alerted me here.
Basically, you'll need to decide whether you want to enhance what you DO in FSX or what you want to LOOK AT

I've found that trundling around NZ, learning navigation techniques etc. is so much more enjoyable with some scenery and weather add-ons. Top priority in this department (if you're NZ based), are Robin's sceneries - plus maybe Roads & Rivers. Also, I found a fully registered version of FSUIPC a boon.
Freeware-wise, WOAI will fill your NZ skies with local AI traffic.