Commander support is a set of skills you will find on the right side of your commander skill tree starting at commander level 62. Maximum support can be achieved at commander level 84 currently. It is important to set up a dedicated preset for support (mine also includes resource help skills) or make sure one of your presets has all of these skills maxxed out before sending support. A lot of people like to add it to their training preset.
To send support, you will also need support kits which you can currently only get from buying packs, but anyone can receive support. There is a skill called the “Support self multiplier” which will make any support you get stronger.
The boosts available from commander support are as follows:
Mobile Ops Ordinance Damage Support: this helps with the tank game and nothing else so I never use it. It is a waste of a support kit.
Production Support: Increases base production; also mostly useless.
Base Protector Defense Support: increases defense on the base you send it to. This is wonderful to have in a battle.
Base Protector Health Support: Same as above but increases health
Base Attack Support: Same as above but increases attack
Research Support: Improves research speed.
Construction support: Improves construction speed.
Training Support: this one is the most often requested and the absolute most useful support. Maximum support with the support self skill active will give you 6100% troop queue and 310% training speed. If the recipient does not have the support self skill; max support is 5800% queue and 290% speed.
When a player asks for support, assume they only want maximum support. If you can not give that, offer them what you have before you send it. A base can only have 1 of each type of support active at a time, and they last for an hour. If you throw a weak training support on a base, they might have to sit there and wait for an hour to get maximum support from someone else. Most will be too polite to tell you that your support wasn’t good enough, though.