I am a returning player myself, luckily I had made quite a few credits in game in the past, I had done mining when Low temp diamonds were making over 1mil per diamond in 2020.
I have tried to have a go at all aspects of the game, in a small amount of time without the requirement of a fleet carrier or higher ranked imperial/federation ships like the cutter/corvette or whatever. At the time of writing this my steam says I have 400 hours of in game time (and some of that was by mistake, I left the launcher open, most of it was on Horizons a long time ago).
My tips to speed things up are simple though
1. Get a ship with a large jump range (Hauler, ASP Explorer etc) engineer the FSD as much as you can. That will help you get around quickly. Transfer required ships when you get far away and log off, come back on when your required ship is where you need it.
2. Don't keep all your ships in 1 place, use a ship to jump around^ keep the ship you need in the systems you need them in (bounty hunting ships for instance, leave it in a station in a system which offers missions where you find res sites).
3. Unlock and use Jameson Memorial - use it to buy ships and modules (it has most in the game at 10% discount).
4. Use websites as tools to help you find what you need quicker, don't waste time. You can make loads of money at the moment in exobiology, and you can set route planners where the distance to the planet is short (reducing the time to get to the planet, scan, land and find life). When you land in a system (stop) and look at the distances (or system map) to find the correct planet without having to fly around pointlessly.
I made an AX (anti xeno) ship and I left it in a system next to another system in Thargoid conflict, and I used my explorer to get to it, then I'd jump into a conflict system (that I found on a 3rd party website) and I used the DSS (discovery scanner full scanner thing when I get into the system) to quickly tune non-human signals or ax combat signatures. I would pickup an escape pod on purpose so that hunters hyperdicted me every 2 minutes and then I'd kill the hunters by giving them hell

before returning to repair and finish for the day. It speeds things up a lot.