I unironically suggest you “just ride” until you find out what kind of cyclist you want to be. You may not want to go down the rabbit hole that is cycling...
But if you do want to embrace the Racer™ Lifestyle, you need the kit, helmet, eye protection, clipless pedals, socks and shoes.
You need a cycling computer and heart rate monitor. I recommend you work with heart rate and not a power meter because power meters are really fucking expensive and you don’t need it yet. I don’t even have one. The wahoo bolt and wahoo tickt heart rate monitor are good. You need to find out your FTP (functional threshold power) in order to find out what your “Zones” are.
I would suggest that first build up your engine first and only ride in zone 2 (long steady rides 2-5 hours). You may find that when you ride in zone 2, you are only going like 25kmh..and that’s okay. Speed will come with time. (If you ever pass a fellow roadie and think “wow he was so slow”, it was be because he was riding in zone 2). After you have a solid base, then you can think about doing work in the other zones and doing intervals and shit to get fast...do a FTP every couple moments to track progress.
The whole concept of beginners doing „base miles“ to build up their engine is oldschool. A lot of oldschool cyclists will do base miles in the offseason...
The newschool approach to getting fit is „Sweet Spot training“. That is cycling between zone 3 and zone 4 (between 84% to 97% of your FTP). You get more bang for your buck. You do more work in less time (1-3 hours). Good if you have less than 8 hours a week. Consistency is everything.
This may seem complicated, but it’s not..Google FTP and zones.
I would not suggest you go on a group group until you are a) have fitness b) have the kit c) have an understanding of riding etiquette when riding in the group.