Depens on so many variables, like your other equipment, your tank, opponent's tank/equipment, etc. In general teleporter first is better, but there are cases in which poison should be bought first (gobo+net launcher for example, or simply playing Antigrav).
Poison first just because of farming is bad in my opinion. I cannot see any advantage in farming with poison (The team doesn't farm better in total if you have a poison magic and you might get into bad situation due to the range as well).
Poison first just because of farming is bad in my opinion. I cannot see any advantage in farming with poison (The team doesn't farm better in total if you have a poison magic and you might get into bad situation due to the range as well).