Loovma Geer

The most powerful chaining trainer is Loovma Geer who teaches you how to maintain your tools and can be found at the Blacksmith. Having more training means that each chain will last more pulls on average and you have a better chance of getting metal back when it breaks. Whether or not you chain regularly, training with Loovma until you're one of his better students is an excellent idea. Your chains will last much longer than with no training and so they are less likely to fall apart when you really need them to work.

Fighters

Since you can't fight and chain fallens at the same time, you'll have to avoid getting hit one way or the other. The most important trait fighters have is their defensive potential by training with Detha, Balthus, or Swengus. Detha is a 2nd-circle fighter trainer who increases your ability to avoid blows. Balthus is a 2nd-circle fighter trainer who increases your balance with a smaller bonus to your defense than training with Detha. However, Balthus can give you more swings if you train with him long enough so you may consider that more important than having more defense. Swengus contains both Balthus and Regia (2nd-circle fighter balance recovery trainer) and is a more efficient way of increasing your balance overall.

These trainers won't protect you against luck hits or against beasts you don't defend yourself against so you have to turn to Histia (increases your health) and Troilus (self-heal) to avoid falling. Since Troilus increases your self-heal by such a small amount yet increases your slaughter rate by such a huge amount that this isn't a viable way of staying alive. If you want to take more blows training with Histia is the best way.

If you are chaining with a healer or healers then it would be a good idea to enable them to heal you faster so training with Rodnus once you get to fourth-circle is an excellent idea. In addition to being healed faster by every healer who is healing you there's also a bonus to Histia. If you want to get additional training after you can't train any more with Rodnus, you can always train with Spirtus in the Town Hall.

Healers

While healers can't train in defense, they have the ability to heal themselves while chaining.

Healers can increase their health by training with Higgrus who is a 1st-circle trainer. Since healing not only takes spirit but health, most healers already make training with Higgrus a priority.

Since chains goes in the right hand the only way to self-heal while chaining is to train how to use the Sylphstone Ring. This is less effective than healing yourself with the Moonstone but fortunately there are several ways to increase your self-healing ability. You can train in Respia which is a 1st-circle healer trainer that increases your spirit recovery so the Sylphstone Ring heals yourself more often. Spirtus who is found in the Town Hall and Sprite who is a 1st-circle healer trainer teaches some of what Rodnus teaches so you can heal yourself and other healers can heal you more effectively. Awaria is a 2nd-circle healer trainer who enables you to heal yourself better and while she is often discounted as a useless trainer, she is very powerful since she makes each self-heal pulse more effective. I have also heard that Awaria works with Faustus but this isn't proven to my satisfaction so I will leave it as a rumor until I can prove or disprove it.

Tools

Shield

The shield can be bought by fighters or made by trained woodworkers (requires two logs of wood and 600 coins) and is held in your left hand and provides an undetermined amount of defense, although it's considered to be relatively small. Anyone can use a shield although I have seen fighter's less willing to do so because one's balance recovers more slowly. The price varies but it's about 1000c new purchased from Wiktus.

Tykan Potion

This potion can be made by healers who have trained in the skill and can be drunk by anyone. Since you drink potions with your left hand you can use this even when chaining. The Tykan Potion heals you instantly for a percentage of your total health which means it's more effective for people with more health. It requires a a pouch of kyten (purchased in the east farms), a cluster of togron nuts (found in grassy areas), and a bottle of water (purchased in the pottery's hut) in order to be made.

Main Gauche

This is a very rare item that is also held in the left hand like the shield but adds a much higher amount of defense and some offense. It's almost impossible to buy one so if you get the opportunity to purchase one, you should definitely do it.