First step, either create a char with 50 poison and 50 alcy. If your using a char that you already have worked on and have a soulstone and have a free char slot, do the above and stone the skills over.
If you have neither of the above options, then buy max poison/alcy skill in haven.
0-30 you can use lesser poison to poison (don't bother with wepons at this stage, you will fail most of the time and you can only poison a wepon once until its charges are out) use a food item for poisoning, food can be poisoned multiple times (doesn't stack).
30-50 you can use regular poison, at this stage food items are still a easy item to poison, even a dagger every now and then to break the monotony.
by this time alcy should be far above poisoning. you will likely gm alcy before you gm poisoning, thus never needing to buy kegs of poison from vendors. (you can reuse a keg over and over)
Once you have reached the point where you can make greater potions, try selling them on a vendor (the gardeners of your shard will appreciate it). the new income will help with the wepons you will buy to advance poisoning
50-85? (sorry can't remember how far it will take you) use greater poison potions. you can use the old fall back, food items, but will most likely not gain as often. daggers and other fencing wepons will be the norm now. at this stage you can sell your newly poison charged weps to other chars for PvM.
Last but not least is deadly poison. get ready this is gonna take a while to finish. Use Wepons to poison.
Hope that this is a bit more helpful.
Just remember there is no Easy, honest way to gm this in just a day or two, it takes time and patience.