there's a couple ways you can approach how you spend your money.
you can buy good or you can buy cheap. work with what you have financially. are you in a rush. how committed are you to airsoft? do you want crispy new or are you cool with wearing someone elses coodie ridden kit on a deal. all these factors will help you decide how you wanna spend.
certain things you dont ever wanna cheap out on.
eyewear - depending on where you play you might need paintball rated goggles due to field insurance reasons. if you're playing primarily on private land than you'd get whatever gets the best seal around your eyes....note...price should never be a real factor for a good fitting set of eye protection. if that means you spend $500 on a pair of custom oakleys than i say do it.
consider the eye seal, ventilation for fogging, do you sweat alot primarily around your eyes and secondarily around the rest of your face. are you able to control your breathing...in the mouth, out the nose (directs moist air away from the eyewear). as far as mesh gogs go, i stay away from them only because you never know what quality of bb is coming your way. it could be a silica bb which wont break or it could be a cheapy that will pulverize on impact which is your main concern with mesh.
given the huge range of eye protection you can get you can be looking at $30 (surplus issue sawfly) right up to over $500 (custom oakley with all the bells and whistles). in between you have paintball goggles and tactical full seal goggles which are like...call it $80-$200ish. if you want full seal gogs than try to find stuff that has a thermal lens (usually paintball gogs)
but this is definately an item you dont want to cheap out on....EVER. ANYONE who says otherwise is a fool and is taking stupid risks with their vision.
this can be very hit and miss. lots of factors in weapon selection to consider. quality, accessories, mag management, power management, in or outdoor, general field fps limits and the capabilities of a particular line of gun to take the power upgrades, availability of parts.
you can easily find an inexpensive clone all over the place nowadays (eeeeeewwwwww) but you'll cry when you realize that you feel compelled to upgrade and your gun doc says "ya...no problem...i can get that done for you but it's gonna cost you $500 to achieve that goal"
depending on how committed you are to airsoft i usually say spend the money on something good out of the box so that you end up spending less in the long run. ie...$600ish on a new vfc scar or a g&p product. spend the money now so you dont end up spending tons later on upgrades and end up having a box of essentially useless parts sitting around.
are you a camper or mover. think hard about this one. it makes a differance. if you camp than you might want a longer gun for barrel length to reach out. if you move than you can easily choose a carbine to help with maneuverability.
what sized battery relative to shooting style. do you shoot semi or do you stand on the trigger for days at a time? again...big differance. guys that stand on the trigger will want something that will accept a large battery purely for charge capacity. you can get away with using mini's if you're pretty light on the trigger. this will affect your battery costs in that you need to plan how many to buy and time spent charging them. spend the money on a decent charger so you dont over cook said batteries. r/c shops can help with that.
also should be a factor in weapon choice since it you're probably gonna get a vest to manage them. if you're picky about what you want to buy in terms of vest/rig/tacticool nylon than you'd probably wanna stay away from a p90 or ump. those are a pain in the ass to stow since they're so long. mag features...g36 and sig mags tend to have locking tabs which can greatly increase your loading times due to snagging on pouches and such.
consider your body when choosing a vest. you probably dont want to be picking up some massive ciras or other full armor styled vest if you're a sweater. you're just going to suffer during the summer. though it can help keep you warm if you play in the winter. a tac vest is leaner and lighter so you can still fit through doors and not knock people down when you turn. also helps reduce snagging on branches and stuff in the brush. are you a wus? a tac vest will easily take the sting off of most shots but if looking like a walking tank is what you want than so be it. what are you planning on carrying? if all you need is mags and water than just get something to meet those needs. dont forget how big you are. not everything may fit you. if you're a horse or a twig makes a differance.
for cryin out loud dont go cheap on these. spend whatever amount you can manage...*note i didnt say can spend...i said spend what you can MANAGE* boots make a huge differance as to if you gonna last the full event or not. comfort, ankle support, gortex if you play in the rain and mud...they come in handy for the odd snake that might wanna nip at your ankles too.
there's huge amounts of things to consider in getting kit...you can spend $500 or $5000 to kit out one person. forget about collecting....gotta give up food for that guestimate
i'm sure there's more i could add but my fingers are getting tired.