I beleive upgrading items is a very easy way to make 50m+ but the problem is you need about 5m to make money using this method. Once you get the 5m go and buy low class armour like 6 sets for rogue (Mainly rogue for cypher) Upgrade it to +7 then add health or dex dousnt matter it sells for 3-5m apeice you can get alot more... And if your having trouble getting 5m then you can kill goblins or cave leeches your choose both pretty easy money... Do not turn in your gems if your like lvl 40 or lower you dont really get nothing good unless you got like 30 gems... And the more money you get the higher items grade you can go. Where the money comes in is mainly in horn crossbow +7/70 sell them for 15-20m theres alot more good items to upgrade them are just some examples. Keep an eye on the smithing bar if it is red there you will have a higher success rate (really keep an eye out if your working with high class items) you can also make +7 rings and ect sell for 10m+
oh... and i found out do not buy from stuff from handmade item sellers there alot more expinsive the non handmade guys sell items for alot cheaper and the hand made items have no special ad ons only says "item name (+1)" lol:)