I'd agree with SΛΤΗΩ on the question of %gain per potion made, with a couple of caveats. First, that applies only to *successful* creation of a highest-available-level potion. Producing junk potions doesn't get you experience. Second, don't be afraid of phlogiston potions for this purpose. I levelled Alchemy as a *third* craft, so I didn't need to use phlogiston potions to gain craft-guild reputation, but they still give experience.
As a side note, to make life easier when levelling up, try to find ingredients that give several of the symbols needed for a particular potion. This way you gain flexibility, thus increasing your chances of making the potion you want. The key is that the symbols in the production interface do not need to be in any particular order, so I can get symbols X, Y, Z in any available order among the three columns that bear the common ingredient. If each column has a different ingredient, I don't get a second chance.
And Ankush, yes, the former gathering professions were merged with relevant crafting professions some time back. Tailoring now includes disassembly of cloth objects and Leatherworking includes disassembly of leather objects, while mining was merged into Blacksmithing. Weaponsmithing is newer still, and includes mining, but the first to be merged, as I heard it, were Alchemy and Herbalism.
Now f2p 60 Xadaganian summy with 60/60/60 tailor/weaponsmith/alchemist, bleah gear, 555/555 runes
Now p2p 28 Xadaganian avenger with 20 weaponsmith
I'm on an extended break from Allods at the moment, but I'm lurking here to keep up with what's happening. From the looks of things in 5.0.02, I'm better off where I am.