Hey OP, check out this magpul mount for your streamlight:
https://smile.amazon.com/gp/product/B00RU12NG6/
It mounts the light higher so it's a bit more out of the way. Also, less bulky than the stock mount.
I have one on my bog and it works great.
It looks like you bought a picatinny adapter for your ProTac light, YSK that Magpul makes an $16 offset that you can thread your light directly into.
It's going to give you a slightly closer mount for your light, shave a few grams, and give it a cleaner look.
Grats man. Be sure to throw a few hundred rounds down range to break it in.
My BCA upper's extractor only lasted about 200 rds before it snapped. Also, my firing pin tip bent. Apparently they had a bad batch of those. Thankfully, both got replaced under warranty but I picked up some extra extractors and a spare bolt from redxarms and I'm using those now.
As for a light, I like my streamlight protac HLx mounted using a Magpul light mount.
That mount is nice because it's less bulky and lifts the light up on the rail a bit so you have more room for your hands.
I'll also second getting rid of the offsets. If you want a decent set of backup sights hold out for the new 3rd gen Magpul's. Should be out later this fall.
magpul has an aluminum and polymer offering if you dont want to wait for an arisaka
If this gun will ever be used for defense, stick with a trusted brand like Streamlight. Their Protac Rail Mount 1 and Protac Rail Mount HL-X models are great. They have scout mount interfaces and include a picatinny adapter, but you can also use a scout mount to MLOK adapter. They come with a clicky tailcap and a pressure switch so you can choose which you prefer.
There's also their TLR-1 HL model which is designed for true pistols, not rifle-platform-pistols like this gun, but you can still mount it easily with an MLOK Picatinny rail. The controls just might be awkward to use.
Olight's are totally fine if this gun is just a range toy. The Olight's "PL" line are for true pistols, not rifle-platform-pistols like the PC charger. For rifle platforms you generally want to be looking at the Odin line, many of which already come with MLOK mounts included in the box.
Would still be dangerously close to your budget.
Magpul M-LOK Offset Light/Optic Picatinny Rail Mount, Polymer https://www.amazon.com/dp/B00RU12NG6/ref=cm_sw_r_apan_glt_i_8XJNCVFVVF23QEQK0AH3
I highly recommend this mount for your light.
I've got one on mine and it does a really good job of cutting down on the bulk of the stock mount.
Link: https://smile.amazon.com/Magpul-Industries-Oclock-Position-Polymer/dp/B00RU12NG6/
The Strike Eagle and the 403R are both good options and will take you a very long way. I suppose it really comes down to what you want to use it for: Red Dots are preferred for close-range shooting and keeping weight down, whereas LPVO's magnification provide a huge advantage for distance shooting, but will provide a lot more bulk and weight than you'll need if your targets are only 50-100 yards away.
As for a light, it's hard to imagine a more perfect option to match your rifle than the Streamlight ProTac HLX, which will run you approximately $100. You can get an improved offset mount (the magpul polymer) for just $17, and you can get better mounting plates for the pressure pad for $30-$45 from Cloud Defense or Shaffer Machining.
As for a sling, there's a bunch of 2-point adjustable slings out there - literally a dozen high quality ones in the $40-$60 price range. You'll probably prefer and adjustable and padded sling. My favorite is Warhorse Concepts, but slings are very personal decisions.
As for magazines, you'll probably want as many as you can afford. A new magazine ban restriction is always around the corner, but thankfully today magazines are stupid affordable. Stick to buying aluminum USGI-style STANAGs or Magpul PMAGs, and pay no more than $10 each (including shipping). Somewhere around 10-20 is a good number of magazines for a primary rifle.
For ammo, you'll want to shoot the cheapest possible .223 ammo for training. For defensive purposes you'll want to decided upon 55-grain, 62-grain, or 77-grain. A really good retailer right now for all of these is Midway, as they're importing Israeli IMI ammo used by the IDF. You should consider what minimum amount of defensive ammo you want to keep, even if that's just 1, 3, 5, or 10 magazines of quality defensive ammo; or if your goal is 1,000 rounds in the back of the closet. You don't have to buy all of your ammo at once, even just two boxes a month adds up by the end of the year.
The last thing you'll probably be thinking about is "tactical gear" and what most people want in this space is a Crye JPC 1.0 or JPC 2.0 for the "tacticool" look. In general, the absolute best super quality gear is incredibly affordable: a surplus Army or Marine FLC ($15), with some surplus Molle pouches ($5 each), and any slick plate carrier underneath ($50-$100) with soft armor ($50-$200) or UHMWPE armor ($250-$400) rifle rounds. And a MICH or ACH or PASGT used helmet off ebay ($40-$250).
I just searched "mlok scout mount adapter" on Amazon and got half a dozen results. This one is what I've been using.
Get the Polymer Magpul one. It's going to work fine.
https://www.amazon.com/dp/B00RU12NG6
You only need the Ariska or aluminum Magpul one if you're attaching an aiming device.
Consider the offset one too, I like mine quite a bit
The HS403B requires picatinny to mount.
The lights I linked to use scout mounts and come with picatinny adapters. To mount to M-Lok you'll need either a section of picatinny rail or you'll need an M-Lok Scout Mount. This is what I use with my HL-X. This is twice as expensive but it'll bring the light in like a quarter inch closer.
I have this also in az. You can have it for free if you want
https://i.imgur.com/ylQeSji.jpg - my 10.5” m-lok rail pistol.
Get one of these: Magpul Industries M-LOK 11 or 1 O'clock Position Polymer Offset Light/Optic Mount https://www.amazon.com/dp/B00RU12NG6
It’s super easy to mount and I really like the position the light attaches.