I really don't get unit organization.

There are thee systems of playing 40k.

"Unbound" Is basically a free for all where you can take any selection of units so long as you have the points for them completely unrestricted. Remember your army points cost must always equal your opponents (unless they want to give you an advantage)

Using the "FOG" or force organisation chart, basically this is how 40k worked before 6/7th edition (old style 40k) and it is still the most common way of creating an army. You take a mandatory minimum selection of troops (normally An HQ choice and two troop choices though some codexes let you take different thing as mandatory) then you can optionally take four more troops and 0-3 of the other unit choices in your codex, fast attack, heavy support and elites. This is how most 40k games are played as it prevents you "spamming" any unit that might lead to cheese or unvaried game play and forces you to play some of the "core" units of your codex. You can also take allies from another codex with a minimum of again 1 HQ and a troop choice then you can take one of the elite/HS/FA The last way is basically "FOG" 2. Normally called "formations" or "decurion style" after necrons "decurion" formation that started it. In this instead of taking the mandatory troops and HQ and then adding on limited additional units you are given a list of units that comprise a "formation" and you simply take the units in said "formation" The formation doesn't have to have any HQs or any troops and you can normally take as many as you want. They often have unique rules that make them more powerful than the units taken alone. Furthermore, "deucrion" style formations tend to behave a bit like the "FOG" in that they are large enough to form an entire army on their own but they have mandatory "taxes" i.e you have to take a certain number of units of this type etc. but again they give really powerful bonuses (the necron one is very good as it massively increases the survivability of an already survivable army) With reference to the collection box, it should have come with a formation, iirc its some battlesuits and some troop choices with additional special move that lets you "wrap" all your units around another one. You basically just bring the units in the formation, any additional options you want/ are allowed to bring, make sure you have equal points with your opponent and boom! you can play.

I think the start collecting tau box and formation has the potential to be a decent 500 point army with some upgrades so if you want a 500 point tau army you basically have one.

/r/Warhammer40k Thread