Mossberg 500, MILLETT???

Alright.. I bought a Mossberg 500 a while back. And I've yet to outfit it with an optic.
As I'm sure most of you know the 500 is an inexpensive shotgun. So I'm not looking to spend much for an optic. I'm thinking $50- $150 MAX. I'd really like to stay around or under the $100 mark. I am aware that you get what you pay for.. That's why I put '150 MAX'.

So I'm looking at my MidwayUSA catalog and they have a Millett Red Dot sight for $79.
It has a 5 yr warranty. It includes weaver style-rings...waterproof, shockproof and guaranteed to withstand heavy recoil. Now i don't know anything about this brand. But between the description and the 5 yr warranty I think it's worth a shot. No pun.
Curious as to what you all think? Any other suggestions?

I have an AIMPOINT for my AR 15. And I didn't mind buying a $500 optic for a $1000 gun.
But wont spend that kind of $ on a Mossberg 500, if yah know what I mean..

Also.. What else am I going to need to buy once I get an optic.. mounts or what not?

I'm still an Newb.. and still learning.. bare with me please..
Thanks

Putting good optics on a shotgun is not a mistake regardless of cost of shotgun. The recoil forces will trash out a cheap glass, or dot, faster than any rifle, while a good sight opens up a new world of slug and double 00 use. Moss 930 Leo prismatic.

I just bought a 500 with brown stock with 2 barrels, slug and a shot gun in a 20 gauge. Have not even shot it yet. I wear glasses and also have a cvs 50 cal. muzzle loader. Bought a simmons scope for it and never could get it set. So i figured it was because i wore glasses. so i got rid of it, (the scope). I latter found out i was trying to set it to far out. Should have started with 25 yards. So i to would like to know what scope to get but for my slug barrel. Please keep me up to date with the scope you purchase and the results.