Exploration pays more than before but not as much as a passenger liner career, nor mining, nor bounty hunting... However as you said you get a non lucrative bonus through wonderful landscapes
CMDR Deyot said most for fitting your ship. The most expensive for your ship will be the FSD as you absolutely want the best one available (biggest A-rated). Next will be your fuel scoop to refuel as fast as possible. You can find a lot in the dedicated Exploration area of the forum, especially this old-but-still-relevant (well, most of it) guide on Exploration Ship building :
https://forums.frontier.co.uk/showthread.php?t=219633
I would also say that mining requests you to sell your cargo at one time (eg when it's full, obviously), so you can't go very far from the bubble. So much for exploring [blah]
For my part, I go exploring weaponless, but with a minimal shielding and D-rate and downsize everything for low mass except fuel scoop, FSD and powerplant for thermal efficiency, with the adequat engineering. Even for thrusters, I try to get the smallest ones while keeping some boost ability. They're enough to cope with gravity up to 2g if you're patient and careful (however never tried more, but other CMDRs did).
Finally, what I can tell from my little explorer experience is that a 10,000 Ly trip will take you ~250 jumps with a 40 Ly jump range, but net you a few millions with a DSS, only by scanning metal-rich, ELW and WW (even if already tagged) ! In order to collect funds to upgrade your ship or buy a new one, maybe you could first start a sightseeing passenger career ? It will let you practise the "jump in - refuel while flying on the other side of the start - jump out" technique
