Weapons: Okay the gun you've linked is fine as a starter, so don't worry about that till you have a feel for the hobby and know what to look for in weapons.
Transparent AKs are practically non existent - i.e. If you look long and thoroughly enough you may find one, but I've never seen or heard of one. Best colour for AK two tones (in my opinion) is the bright orange since if you squint at it then it almost looks realistic haha. Cymas are brilliant but you will need a spring downgrade as they clear 370fps out of the box.
Chest rig/Loadout: Best thing to do is to decide what you need the rig for then choose accordingly; chest rig/vest for CQB games or plate carriers if you decide to milsim/use low cap magazines. It's all dependent on your ideal budget as well since most decent chest rigs/plate carriers cost in the region of £40+ before you add on pouches. If you're on a budget then a prebuilt tactical vest may be a better choice as you can get a decent one for around £30. As a new starter it's unlikely you'll be running more than a couple of high caps so just having camo trousers on is enough as most pockets on these are big enough to hold magazines. This brings me on to the chinos. Don't bother with them and buy a pair of surplus camo trousers to wear instead (can get them for less than £10).
Face mask: Depends on personal preference and your sites restrictions. Most ask for under 16s having a full one piece mask, 16-18s can have a lower mesh mask/goggle combo and 18+ can just use goggles. Personally speaking the goggle/mesh mask combo is my favourite combined with suitable head wear. I use these two products as my face protection:
http://www.tactical-kit.co.uk/smith-optics-elite-boogie-regulator-goggle-10085-p.asp
http://m.ebay.co.uk/itm/370897157295
Boots: Anything sturdy with good grip is your best bet. Hiking boots are cheap and rugged but again it's down to what your comfortable in. Most commercial trainers won't take the abuse of regular skirmishing whereas a good pair of boots are usually cheaper and last a lot longer.