Wouldn't recommend hi-caps myself, I'd rather buy a box of mid-caps. Hi-caps are useful though for if you don't mind about winding and rattling.
In terms of slings, depends on your preference and budget.
Single points, two points and three point slings all have disadvantages. If you're short for example a one point sling isn't great, and your rifle is flapping around in front of you. A two point is good because it is across your chest and you can sling it over you back.
You could get a Magpul MS3 replica for only $13 here (I've bought from AirsoftPeak loads and they're great)
http://www.airsoftpeak.com/multi-mission-bungee-rifle-sling-system-black-p-9587.html
Wouldn't recommend any other cheap slings you might find on eBay / Amazon. I bought a cheap two point bungee one and it doesn't feel very good quality. My ASG bungee sling (single point) on the other hand feels very good quality for ~ £13 but I don't think it's the type of sling for me.
Looking at a picture of the Raider there's the front sight post sling swivel and two slits on the crane stock to stick a sling through. Doesn't look like it comes with a sling plate but you can buy one inexpensively. There are also Picatinny rail mounted sling loop things, you can buy both here:
http://www.airsoftpeak.com/slings-swivels-c-444_561.html
Not sure what quality will be like but they're usually fine, and if you see a style you like you could try to find the real steel version or something which will be stronger.
Don't apoligise for the questions mate, it's what the forum is here for.