For me, I'm still not good and it's been close to a year of playing, as well as casual play prior to that. I set a goal for one PR per day in 2018 and still have it going, some levels I haven't gone into much or haven't needed a tutorial yet (such as Statue, one of the worst levels IMO). That said I've gone through most stages 5-6 times or more and my overall skill has improved a lot, I have cut more than an hour since I started tracking my total time. I haven't spent more than a couple hours per PB except a couple cases, usually I can play 20 mins or so on a level that's ripe for improvement and get the PR.
I only got my first points this week by grinding out a hard level most people skip, but I got Bunker 1 :18 within a week of playing that level while I was new, which is a reasonable time formerly worth points. If you specialize to try to get points such as Dam or Runway Agent, you'll probably be able to get them but it will probably be boring AF. I think 6+ months is probably a good estimate before you'll be solid enough to get a range of times worth points, depending on your dedication and the levels you play. If your goal is points from the start it will probably be less.
I suggest you pick a goal and try to stick to it, that's really the biggest barrier in GE speedrunning, perseverance. OCB and skill will build as you play the levels over time, and knowledge is also hard to take in all at once so it can be good to learn at your own pace, try outdated strats for completions, and set goals based on your own times, not the WRs unless you really want to go for them. Agent is super optimized, so playing SA and 00A can usually be worth it as a new player to get better total time and for variety.
Also, it's good to grab a Japanese cart for playing 00A and certain levels, but it's definitely worth playing on a CRT if you can. I still have some PBs from playing on an LCD like Bunker 1 18, but I feel the CRT is an improvement in every way and prevents a lot of stucks and poor lines. The game lags enough as it is, the TV can at least give you an accurate timing. GL and feel free to share progress or ask questions, other new players often struggle with the same stuff.