The most common goal in alchemy is to create a healing agent which has multiple uses and is easy to carry around. While it's certainly possible to carry around 20 pieces of georin grass, it's a lot more convenient to create a salve which has 20 uses. Not only does alchemy result in a a simple to carry item, but it may indeed create a more powerful healing substance than in its rawest form.
Some herbs, such as jadice, seem to be best used on their natural form, that is just as a jadice flower as opposed to a jadice potion while others, such as nilos grass seem to benefit from alchemy.

It should be noted that I use salve and pulp as examples. Processes on the herbs, such as drying, as well as the type of herb itself, will result in different types, such as potions or mashes or powders.
In order to create a potion or a salve, you'll need to have three basic ingredients: the pulp or powder of the item you're wishing to create the salve from, a catalyst and water. For the first part, you'll generally want to grind down the item in a mortar. For example, with georin grass, simply put grass in mortar then crush grass in mortar with pestle in order to turn into a pulp. It may take more than one crushing in order to turn into a pulp, but you will eventually end up with some georin pulp in your mortar. Next, you'll want to take the pulp out and count my pulp to make sure you're certain of the count. I have no reason to believe that the numbers will ever change, but there is always that possibility.

Once you've covered the pulp, you now need to deal with a catalyst. Catalysts come in several flavors: dracon crystals, glaysker flower, seolarn weed, and tukai stones. I've not had much luck with the latter two, so I suggest you spend the coin at the local-most alchemist and purchase yourself some dracon crystals. Once you have the crystals, you're going to want to make a powder out of it. This is done in the same fashion that was used to crush the georin grass. Put it in your mortar and crush at it for a while until you end up with some dracon power. Again, I have no reason to believe the numbers will change, but you should count the powder to make sure you end up with 10 pieces. There is also an odd 'feature' of dracon powder in that in order to combine multiple pieces of dracon powder together, you needn't name them individually, simply hold a piece of powder in each of your hands and combine powder.

With the two parts settled, you'll need some water to turn your pulp into a salve. You can either use the free water listed there or just purchase it at the alchemist. The alchemist in Crossing seems to charge 12 copper for one unit of water. With the water, in order to combine it, you'll need to pour water into mortar for instance. This will take the water that you had in your hand and lump into another water sitting in your mortar, giving you a water that is two pieces.

One of the most important parts to remember about mixing in alchemy is that you need equal parts in each of your three ingredients and the three ingredients must all be in a single item. That is to say, you must have some water, some dracon power, and some georin pulp in your container and each one must have the same number of pieces in it. The number of pieces is a 1:1 correlation to the number of uses the resulting salve will contain.

All of the parts should be combined into either a jar or a gem pouch, then mixed somehow. Gem pouches can be closed and shaken, resulting in a salve in the end. A jar, or any other container without a stopper, can be mixed using a mixing stick. It may take multiple mixings or shakings in order to get a salve, but eventually you'll end up with some georin salve that should have a number of pieces equal to that of the original pulp.

• A pestle and mortar
  Used for crushing herbs
• Dracon Crystals
  Best catalyst around
• Jar
  There are multiple jar types, those with stoppers and those without. For the purpose of convenience, the ones with the stoppers are the best but tend to be a little flashy. A normal jar and mixing stick are a fine, and cheaper, alternative
• Vial
  Both vials and jars can be used for capturing water, so you don't have to pay for it. A must for cheapskates
• Wayerd Pyramid
  Used for drying herbs. Not very convenient to carry around, so I don't suggest buying one unless you intend to sit around for long periods of time mixing up potions
• Portable Stove
  Used in alchemy, but of questionable use. It's bulky, it requires coal and it doesn't seem to add much. I'd suggest not getting one

Most alchemist shops carry the most basic items you'll need, such as a mortar, pestle, and jars. If you want some more interesting items, there are a number of places that carry customizable or more rarefied tools. The alchemist on Aesry has a number of options for their pestles and mortars such as:

Obsidian, Black Basalt, White Marble, Green Marble, Pink Granite, Stained Marble, Blue Coral, Red Coral, Driftwood, Green Glass, Cobalt Glass, Cranberry Glass, Streaky Glass and Smoked Glass.

Horse Clan sells a number of attractive stoppered jars, pestles and mortars:

a coiled red firecloud clay jar painted with a black-on-white sunburst design, a coiled black firecloud clay jar circled with a white whirlwind design, a coiled blue firecloud clay jar etched with a sweeping curve of dragonflies, a coiled black firecloud clay jar incised with a rainshadow design, a coiled red firecloud clay jar painted with a swirl of white tadpoles

a quartz-glittered mica clay pestle, a black-glittered mica clay pestle, a silver-glittered mica clay pestle, a gold-glittered mica clay pestle, a red clay dragonfly-shaped pestle, a black clay dragonfly-shaped pestle

a black clay mortar sculpted as a badger coiled nose-to-tail, a blue clay mortar in the shape of a laughing frog, a red clay mortar in the shape of a sleeping tortoise, a quartz-glittered mica clay mortar, a black-glittered mica clay mortar, a silver-glittered mica clay mortar, a gold-glittered mica clay mortar

a large black firecloud clay bowl incised with a rainshadow design, a large red firecloud clay bowl painted with a circle of tadpoles, a large black firecloud clay bowl painted with dragonflies, a large blue firecloud clay bowl etched with a whirlwind design

It would seem that all herbs vary in the number of pieces, but you can influence it positively by foraging careful or precise. Generally speaking the number of pieces goes up with the use of precise or careful. Flowers that I found around The Crossing, as well as hulnik grass outside the west gate, were 4 or 5 when foraging normally.

A few hints worth mentioning with regard to alchemy. Pulp can be replaced by whatever object it is you mean to use.

• break <pulp> -- Results in the pulp being broken into equal (or rounded) halves.
• break <pulp> piece -- Results in you breaking off a single piece.
• combine powder -- Used when combining that pesky dracon powder, as opposed to combine powder with other powder.
• combine flowers -- Combines multiple flowers.
• pour water into jar -- For combining water.
• combine pulp with other pulp -- For combining two pulps together.
• Dried herbs end up more potent than non-dried herbs. Have a ranger beseech sun to dry on herbs or use a wayerd pyramid for that extra kick.