From Level 26 to level 1500, every 5 levels, you can find the Greedy Demonling on map. The first few give 3 bottles per defeat before building up to the maximum of 5 bottles each for the remainder of fights.

The wiki has good info but i thought i put in some quick pointers

Catalysts are not only bottles. There are so called luck potions which give 2,5% chance on the chance of the recipe to proceed, most of the time that will eventually still have 1% fail chance which is inevitable.

Make one or a few of the luck potion recipes from each color so you can check if you have lots available of another color when you run out of the preferred materials.

In middle to late game a lot of the level 5 and level 6 gear will be available from farming chests n siege, reward chests for bigger farmbosses drop ou equipment chest. So don't force yourself to put a star on every one of your heroes, just focus on your main dps and bridge heroes, or Siege mains ofc.

I promise you get those level 6 rings easier than you think, you just have to wait :D

In every other case its cool to craft the items as you go on, have the recipes ready if you need them can fill a lot waiting game when a timers is slow or you have some time to killl. but only make sure you have enough of that material, talk to your clan mates about it, they might have some pointers about the item you think of making.

But generally leave the crafting alone until you get to about level 3000 as you then have reached the stage where the portal looses the early stages equipment parts and if you're used to have enough level 1 shoes to push those daily hero sacrifices for more shards from the altar, you will have to craft cheapies now. :)