Gems: synthesis&socket

how can i use the most economically gems?
there are gems lv 1 and higher.
gems lv1 can be synthesis together.
how many gems can be join together?
Is armour with socketed gems lev2 or lev3 can be use by hero basic-level ?

Here's what I do and how I use them.

For your front line defense (swords always) I use defense, vitality and agility gems.

For you ranged attackers (muskets, siege, etc) I use attack, leadership and either defense or vitality.

If you don't have one type ALWAYS at least outfit them with something if you have it, it makes them much stronger.

As far as synthesis goes, as long as you have 4 of the same type and same level you can always put them together. 4 level 1 gems make a level 2. 4 level 2 gems make a level 3. But, don't go crazy when starting out because it's honestly better to put 4 level 1 attack gems on a ranged musket than it is to put 1 level 2 attack gem. So until you start getting a lot of gems and everybody has them, then don't even worry about synthesis.

And you can put gems on any hero... just make sure you take the off before you destroy equipment and always remove them from the basic hero and put them on your champs as soon as you can.