In Brief
- Buy and apply stacks of 99 Bronze Crystal (L) bought in Ethereal Est
- Requires Gold 16.75M from a base weapon
- 30-100k gold per battle (floors 1-100) in Hell Dungeon on Easy.
- Save your RDP for the Ultimate Crystals (500 RDP) in the shop
In Detail
During the end game you can buy stacks of 99 Bronze Crystal (L) in Ethereal Est for 490k, with a fee of 98k to then apply it to your weapon.
Each stack will net you 35 levels, so for a base weapon this is going to take about 28.5 stacks, or 16.75M.
In reality it will be less than this due to crystals you get through drops. (Many Gold Crystal (S) drop in the Hell Dungeon.)
I'd advise not breaking down items for crystals as the cost will generally outweigh the benefit without a lot of reloading, and the time that takes is far better spent killing enemies for quick gold.
Each battle in the Hell dungeon on Easy around Floor 90 will net you about 100k, so this is pretty easy to farm. (Earlier floors with start at around 30-40k and increase as you go deeper). I had enough gold to do this simply by making my way to floor 100 for the achievement and not skipping any battles.
Save your RDP for the ultimate crystals in the shop. Though purchasing a Super Rare Gem or two can help with crystals from drops. (Unsure if this is more efficient than just buying Ultimate gems though, as you need 20+ Gold Crystal (S) to equate to one Ultimate Crystal).
With any sale price (Merchant) ores, try and break them down and put them on one weapon. Each ore can reach 70-72% sale price when put on a weapon (reload to get this) so 2 or 3 of these gains a lot of gold when selling weapons or Large Gems (You should only sell these at end game when you have this).
Note: the x3 EXP DLC will make this much faster, as you can generally auto battle (gaining kills for the 5000 kill achievement as well) every fight and will fully heal / gain at least one ever every battle.
If for some reason you are short on gold then stick on the encounter ring and battle each step and it will go even faster. You'll need to do this for the 5000 kills achievement anyway.
NOTE: The easiest way to beat the Guild Hero is using Fleons Gold rush attack, high speed (Level 300+, x4 speed 3 Ors at 100% on a weapon) and equipping an Undead Gem. So don't spend your gold until you defeat him, or keep a separate save.