For a entry-level gaming mouse the Razer USA Razer DeathAdder 3500 dpi is one of my absolute favorite options. At the $100 mark it's a fair price for what you're getting with the speed and dpi sensitivity. The longevity varies, I've gone through two in seven years personally, but I know people who've had one just as long, and people who go through them in months. I used this mouse to hit diamond/challenger in league in s2/3 and have been able to be in the top 100 NA in PUBG with it as well. It's definitely good enough to get into professional-level gaming and more than enough to get started!
I've had this keyboard for the last six years and it's been quite great for me. It was pretty affordable at the hundred dollar mark and has filled all my gaming and editing needs in the time since. Around year five I started having a few minor bugs with the 't' and 'r' keys sticking, but taking the keyboard apart for a quick cleaning fixed the issues. Slowly losing the original punchiness of the mechanical keys, but after half a decade i'm more than okay purchasing another.