well my advice is that the first thing that you should buy are a Good set of Goggles, a set of JT paintball goggles are what a lot of airsofters in and around my area use.
Next you want a set of Combat boots or jungle boots,(jungle boots are better for warmer weather type of play so you feet don't over heat and sweat) and lastly you may want to buy some camouflage clothing, I suggest maybe going with either a woodland or olive drap, as those are the most common types around.
after that just do you research on the different AEGs and there merits and flaws , what is in your price range for the moment.
when you are ready to get out to the fields, ask before hand if you can see if any one can loan you a vest and an AEG, as you will not learn what type of gun is best for you till you have had a chance to get a feel of the gun it's self.
also till you know what sort of gun you will be fielding, you won't know how to configure your vest. because if you field a P90 over let's say a AR/AK or a M4 or M16, you won't know what type of Modular pouches too buy for your vest.
As different AEGs use different types of magazines and because the different magazines are different in shape and size, the need different types of pouches so then can be carried around.
P90 mag's are longer and thinner, while an AK47 mag's has more of a curve in it's shape. M4 and M16 have a curve to their body but not as pronounced as the AK47 mag's.
hope this is of some little help