Here's some tips then:
BB's:
Never buy your BB's too cheap, it might seem like a saving at first, but they are cheap for a reason, some of them may not be perfectly spherical, and if one jams itself in the hop-unit it can strip your gears or the piston, and they have been known to damage the hop unit and inner barrel aswell, all of which will cost a fair bit to get repaired.. it's just not worth it, good quality BB's are not all that expensive, but AEG repairs certainly can be!
0.25g BB's are definately the standard, they just plain perform better in an AEG than the 0.20's, hence 0.25's are the most popular, but it's a good idea to also have some 0.28g's in reserve, on a really windy day, that extra bit of BB weight can easilly be the difference of hitting the target, or watching the BB's sail past the guy due to a cheeky side wind.. they are not a requirement, but nice to have!
Batteries:
Don't cheap out on thease either, or the charger for that matter, this is where the AEG gets its power from, so using a crummy battery is a bit like wading into combat with damp gunpowder, and you
will be dissapointed with the guns performance, moreso because you will be needing the stick-type battery in that 74U, thease are small cells, so they have to be of good quality to do anything usefull.
You can ofcourse use the supplied one just to get into the game and get a feel for it, but replacing it with a good one is undoubtedly the best upgrade you can do for this gun, and i would highly recommend it.
I'd recommend replacing it with a 9.6v stick battery, made of cells that deliver atleast 1500mAh, sticks made of "Elite 1500mAh NiMH" cells are excellent, i use them myself, but i can also recommend sticks made of "
Intellect 1600mAh NiMH" cells, both of thease cells deliver lots of power, and they won't get sluggish untill they are allmost compleately drained, they are ideal for Airsoft use.
And get a good charger that can detect the voltage it needs to supply, and most importantly, will automatically stop charging when the battery is full, a bad charger can quickly ruin an excellent battery, so it is not a place you want to save money, it will cost you more in the long run, constantly replacing broken batteries aint cheap..
Magazines:
As a genereal rule of thumb with Airsoft AK magazines, you can cheap out on hi-caps and Low-caps, but not on Mid-caps, cheap mid-caps tend to be very.. rubbish.
If you want to keep things cheap in the beginning, go for some Hi-caps, the CYMA ones seem to work fine in standard guns (they do have feeding problems in hi-speed tuned guns though), they rattle, they need to be wound up, and i woulden't recommend dropping them on concrete, but they work and they don't cost much, so it's a good place to start if your on a budget (and with hi-caps, you only need one or two, so you don't have to invest in mag-pouches or chest-rigs, which lo and mid caps will require).
But eventually, you will probably get sick of hi-caps, most people do, and by then, you should know better if you want to spend more money on the hobby or not.. and if you do, i'd recommend you get some G&P or VFC AK-74 mid-caps, they cost a bit, but they are worth it, they are sturdy, they feed well, and they look quite good too, so they are worth having.
Safety:
Forget the goggles, Airsoft guns wont just damage eyes, they will also break teeth and earlobes, and as a beginner, you will make beginners mistakes and get shot a lot, so my recommendation would be to start out with a full face mask, Airsoft should be fun, not a painfull reminder of how you lost two front teeth, so better safe than sorry.
Goggles are an option, but not a cheap one if you want to be kind to your face, as you will need a lower of some sort, be it a Nomex lower + toothguard, or the cut-out lower of a full mask, or one of thouse special mesh lowers.. well, neither of them are cheap.
Also, avoid masks/goggles with mesh infront of the eyes instead of hard plastic lenses, mesh works fine for Paintball, but Airsoft BB's will shatter when they hit it, and tiny bits of BB debree can penetrate the mesh and hit your eyes, so yeah.. not the safest thing.
Gun care:
Stop shooting if BB's are nolonger leaving the barrel, AEG's do not like to be dry-fired, they will break if you do it for too long, also, stop shooting emediately if the gun suddenly changes sound (be it that the report sounds more hollow, more like a thud, if the motor seems to make a strange squeal, or you hear strange grinding noises, anything along thouse lines), this is allways bad news, it means something is stuck, broken or about to break.
If it happens, check if the barrel/hop is obstructed, if it is you can clear the obstruction and keep playing, if not, the problem is in the gearbox, and the best you can do is call it a day and go get it fixed, because if you ignore the problem and keep shooting, then whatever has broken will fail and take something else with it, making the repair costs much worse..
The hop unit contains a small rubber tube, and like all rubber, it dries out and cracks if left to it's own devices, to stop this happening, we use Scilicone oil to lube it, that stops it drying out.
They sell the stuff in all Airsoft shops, but they also charge an arm and leg for it, you can buy it much cheaper at your local hardware store, just make sure it's "Acid-free", and it'll be the exact same stuff you buy in Airsoft shops, just much cheaper! considder that my super-saver tip of the day!
And that's really it then, remember to call your hits, nobody likes a cheat, but everyone likes a good sport, treat your gun with respect, it may be "a toy" but it doesen't look like one, so try not to get into trouble.. and above all, have fun, because that's the whole point of Airsoft 
