First, collect legendary trash equipment from the world. You can start with level 40 and above. Each piece costs 200,000. Collect level 40 ones and dismantle them to get 5 orange gems. Level 45 ones can be dismantled to get 7 orange gems. You can also get orange gems by trading in the world chat, for 30,000 or 40,000 each, depending on your situation.
Every day, purchase four or five pieces of trash legendary equipment to dismantle, or collect 40 orange gems. That's basically enough to perform ten tries. Take the gems to the merchant next to the auction house in the city. You can exchange orange gems for items that can open level 45–50 legendary equipment. 10 orange gems can be exchanged for one item, with a daily limit of 10 exchanges. The properties of the legendary equipment obtained are random, as are the types, and it's very possible to get top-quality items.