Hi Sparky! Welcome to the sport!
Drakker has his list and it's pretty good. I personally disagree that a radio is a "basic" necessity, but everyone has different priorities. I own and use a radio, but I don't think of it as a "basic". I'll give my take:
Absolute basics (assuming you're running AEG (airsoft electric gun) as you've indicated):
- Gun + magazine
- Spare magazine(s)
- Barrel cover (also called a barrel "condom")
- Full seal eye protection (typically goggles, but can also include masks) with ANSI Z87.1 rating.
- BBs
- BB loader
- Battery charger
- Decent footwear, suitable for the terrain you want to play on
- Kill rag
- Gun bag or case - Some people carry their guns in hockey bags or soft-sided carry-on bags - it doesn't have to be a dedicated, military looking "gun bag".
With these items in hand, you should be able to play at any outdoor or indoor field I have experience with in Southern Ontario. If you are missing some of these items, you will either not be able to play, or not be permitted to play on some fields. For example, the barrel cover is required at some fields, as are kill rags. Not all fields require full seal eye protection (often abbreviated "eyepro"), but a fair number do. Also, for the safe and non-disruption play of the sport, ensure you always transport your AEG inside a closed bag, gun bag or case - don't make the newbie mistake of carrying around things that look like real assault rifles anywhere in the open, even to and from your car to a store or field. Keep your gun in your bag until you are kitting up to play or taking it out INSIDE a store with the knowledge and permission of the store staff.
As for clothing, jeans and a grey, black, beige or forest green T-shirt or long-sleeve shirt work fine. I've seen people play entirely effectively in sweatpants and sweatshirts.
Next Step
Beyond the basics, the next steps I recommend are:
- Gloves(tactical gloves recommended) - strangely, "Mechanix"-brand gloves are both popular and cheap, available at Canadian Tire, Lowe's and Home Depot. Gloves help reduce the sting from BB hits to the hand, where knuckle strikes are both common and painful.
- Good, all-purpose set of camouflaged clothes or battle dress uniform/advanced combat uniform. These are not at all necessary, but they can definitely improve your ability to be stealthy (more important than camo is technique and movement, but that's another kettle of fish). There is a bewildering array of patterns out there. Researching them is helpful. If you can't decide, "Multicam" is an excellent all-purpose pattern that is a very common choice among today's players. Older patterns, such as the still very effective US Woodland/M81 can often be purchased cheaply at surplus stores for $30 or less for each item of pants and combat shirt/jacket/blouse. I once found a pair of Woodland pattern pants by Rothco, a cheaper but not horrendous brand, for $10 at a Value Village.
- One-point Sling -there are differing schools of thought on what types of sling are best. Research it yourself, but a one-point sling is simple and effective. Having a sling will save you all sorts of arm fatigue if you're playing longer outdoor games or games where you have to walk out to the field.
- A chest rig or battle belt (also called "gunslinger belt" or "tactical belt") for holding extra magazines. If you are playing typical skirmish games which permit mid-cap magazines or high cap, you're not typically going to be running out of more than two magazines during a game... but some fields expect you to play two or three games before you get a chance to go back to the staging area. In these cases, something to carry three to four (or more) extra magazines is very helpful.
A common very basic set-up for a chest rig or battle belt is enough pouches for between three and six magazines, an "admin pouch" for carrying assorted items like kill rags, snacks and loaders and sometimes one or two other pouches as required. Make sure your mag pouches fit the magazine models you use - you may not be aware that AK magazines don't fit easily in M4 pouches, or that G36 mags hardly fit in anything except for double pouches or specialized G36 pouches. You have an M4, so your life is much easier.
- Good red-dot optic. As far as I can tell, the model of the G&G CM16 Raider that you bought doesn't come with an optic. A decent red dot helps with situational awareness and helps you get your barrel on a target faster and more easily. You won't need magnification until you get better at marksmanship and tactics, so don't bother with a magnified model like the ACOGs or various short-dot/sniper scope clones. And anytime you get an optic, get a lens protector. I've personally seen three people get optics cracked or smashed during games where I was playing, and many more games where the protector was broken but the optic was saved because of the protector.
There are many pieces of gear to expand beyond this, but the first list above is what I would view as the basics, and the second list is what I would view as "basics-plus".
Have fun with the sport and remember the fun of the game is actually playing and playing well, not what gear you own. (Though that is definitely fun too!)