Even if the thread is a bit older. I would like to add a few things.
Ok, so for me this is what the game is all about, the exploration.
So if I understand you well, you wanna go into deep space and discover new things. The Cash is not the main objective, but comes automatically.
1. Finding planets and DSS of planets is only a small part. Go out of the bubble, and you will find systems, noone has ever been before. Scanning objects within the bubble is a waste of time imo. 6K Ly outside the bubble gives you easily spots, where you hardly find any names of other commanders stamped on the planets (unless you head directly towards Colonia). I find it quite satisfactory, to find a system with an earth like world, where noone has ever been before. I usually scan the entire system in that case. But this is really hard to find. I read, there are/were ELW hunters, that only checked for ELW and nothing else, jumping only to systems with the highest probability. If I would make a guess: within 2-3K LY from the bubble, its almost not possible to find an undiscovered ELW system. Look as well for terraformable planets. They give lots of cash DSSing them. Unfortunately in the DSS you dont find straight away "interesting" things, like terreformable, so you have to check briefly the info of the planets in the system overview.
2. I needed literally years

, to find out, that the Codex is not only informative, but you can actually find and confirm (and get cash) all the different planets, stars, xenos, geysirs and biological things. Each time you find something (for you) new, you get an entry in the Codex and a blue hook, next to what you discovered. Not only that, you can do this in each sector of the Galaxy seperately. (Bubble is the inner Orion spur e.g.). I would say, this is a lifetime challenge!

3. If I remeber well, after scanning landable objects, you might find new signals on the surface. In my latest run into deep space, I accidentally found two emergency signals on an unimportant moon. Found in total 6 rescue pods and brought them back into civilazation. Dont ask me, why I scanned this moon. Just felt like....
4. Check for signals in the DSS. Occasionally theres more than planets to find in a system!
So what do you basically need?
Fast ship for sure. High end I read is 50 LY per jump with the diamondback or ASP explorer. 45 is already quite decent. But to get there, you need engeneering. Basic is about 40LY if I remeber well. Dont install useless things. Many modules are only C or D to save tons. No lasers. I also take a reparing module just in case. Never needed it so far. And of
DSS scanner is a must.
And a bay for a rover, because you might have to exit the ship to scan geysirs or take cargo.
And very important too, a very good fuel scoop. I installed a 6B in my ASP. With the fly-by to the next star I scoop the entire usage of the last jump.
Final tipp: I read somewhere, that some ppl scout well known routes back into the bubble, just to hunt down other players. I dont know if this really happens, because I read so much about player hunters, and allthough I play always open, I never met any. But coming back from exploring I go into private mode. Get destroyed before delivering the discoveries, makes you lose all! I wouldnt take any risk here.
I am only an average explorer. I am pretty sure my knowledge is only basic and many other commanders know much more about it. So to everybode else, fell free to add something or correct me, if i am wrong. Still learning!
And last but not least: I play the game in German

, so i might use some terms, which are not exactly correct. I hope you know what I mean.
Live long and prosper my fellow commanders.
Edit: Edited the typos and added fuel scoop.