Mine came with iron sights and I use a red dot made by Walters, there are better out there but it didn’t break the bank. As an aside I found a short extension so I could properly mount a bayonet. I also put magpul furniture on it.
I have S&W M&P Sports II. I’ve gone through 30+ hours of training courses firing 2k+ rounds and no problems. You can get one for about $500 and it’s more accurate than you’ll be for a long time. Buy extra magazines, a two point adjustable sling, and a red dot then take training and that will tell you what else you need.