By far, the easiest way to get as much Tinerium as you need is to use the Dislay Table XL and put in "MIXED" items. That means to mix up several types of transmutable items. Gems, Metals, Relics, Space rocks etc.
Just make sure you have at least two different types on the table at the same time. NOW add up all the values of the items on the table. You want the total value to be between 3,500 and 4,999 for ALL the items. When you hit combine, you will get a small spire cut tiberium. Set it on the ground and let it sparkle for a little while and it will grow into a large spire cut worth between 30k and 45k simoleans.
If you save up 3 large tiberiums and then fill the table with other items (mixing types again) so that your total value is over 100,000 you will get a bottle of nectar worth 75,000 to 110,000. This will rise in value about 2.5% per day if you have it in a fancy wine rack stored in a basement. You lose a bit of value at the start, but before long, that bottle of nectar will be worth MUCH MUCH more as its value compounds similar to the compendium.