If you want to try getting a few extra tokens on the side, or a lot if you're lucky, then fishing is good for you. Fishing takes patience and quite a long time for you to see the benefits of it, but I fished apx. 100m tokens before going into M1.
First thing you want to do, to start fishing is do /fishingrod and /warp fishing
The command /ce will allow you to view the enchantments to you can apply to your fishing rod.
I recommend starting with the 'Fish Doubler' enchantment, which allows you to get 2 fish per pull, instead of 1. This will allow you to make a little bit more money from selling the fish, aswell as it will complete your /ach for fishing faster.
Next what you want to get is unbreakable, if you have the spare tokens, although I don't really recommend this as the 2nd enchantment, seeing how you can fix your rod for 100 tokens, but it does help.
KeyFinder is very important on the rod, with a maximum of 12 levels, and that is what you want to get next. It's not as expensive as CrateFinder, and level 12 KeyFinder gives you the chance of finding M+ keys, which help you with the next enchantments on your fishing rod, or your pickaxe, whichever you prefer.
Next is the quite pricey, but well rewarding CrateFinder enchantment. With 20 levels, this is one of the more expensive enchantments to finish completely, but level 20, gives you the chance to get UltraDank crates from fishing.
Then come the last enchantments which are all additional, and they're not mandatory to have on your rod such as, autosell, which does help out, so you don't have to shift + right click every time you want to sell, EXPExchanger, which changes your EXP into tokens automatically, KeyUpgrader and CrateUpgrader, which automatically puts 4 keys / crates together, and upgrades them into 1 higher-tier crate / key and also Nightvision, which is self-explanatory.
Also, with the recent updates, you have the chance to fish LuckyBlocks / LuckyBlocks+ and LuckyPetBlocks, although the chances are very slim. + You can fish out token vouchers / dragon lair time vouchers and dragon lair booster time vouchers, which is pretty neat.
Apx. token price to max out a fishing rod with all enchantments, is 3.5 - 4 million.