Hi and welcome to Project Entropia
For your question:-
1. Currently, the 'decay' for armors are based on the Dmg absorb. Choosing an armor set is usually based on your budget
25ped-Pixie
125ped-Rascal
200ped-Knight
500ped-Vigi
1300ped-Nemesis
Each armor 'set' has diffrent types of protection, try checking
www.pe-addict.com for armor charts
*Note the decay in the above site no longer counts, as I wrote above all decay on armor is based on dmg absorbed
2. If you're a beginner, use the Solomate Opale (available at the Trade terminal). My recommendation is use the Opale and get an amp A104 (cost abuot +5). Once you Graduate with the Opale (meaning u do the highest minimum dmg, hit abilty, critical), stick the A104 on the carbine. Its a very nice and cheap gun
3. Well there is no 'GEN bot' in PE. I think you mean Drone 'Generation' 01
Drones do Burn and Penetration and Burn Damage.
Opale+A104 in Rascal should be a cheap setup to kill them
4. To find prices on items try
www.pe-trade.net (Type in the search, what item u want). It will list the previous 'bids' on the item you search. This will show you the 'market value' of the said item.
For stackables (Ie.Hides, Ores, Enmatter,etc)
www.mytwopecs.com
Good luck.