It would seem a simple question.

The simple answer is when you need it, and that's the complicated part.

Each invader drops five  different invader materials, you have to decide which invader equipment you want to go for, and why.

The answer could depend on your playing style and your game experience in general, but also what occurs during the game

You also have to take into consideration that the invader you want to attack may take time to appear on the global map, and that it could take some considerable time to collect all that you need just to complete one piece of equipment.

It takes 1256 (edit 1024) simple items just to make one legendary item, so you also have to decide whether to build equipment from the simple items, and use them straight away, or wait till you have the equivalent legendary, its your choice which is more beneficial. 

Look at the game tutorials and the  information on the internet, but consider that some of it might be out of date .

I'm sure you will get others answering your post.

xyz said:

It takes 1256 simple items just to make one legendary item, 

wrong :

it's 1024 (1...4...16...64...256...1024) 

Man2Hell said:

xyz said:

It takes 1256 simple items just to make one legendary item, 

wrong :

it's 1024 (1...4...16...64...256...1024) 

Sorry you are right, I couldn't find the list and I guess remembered the figure and got it wrong,

in fact that number probably stuck because I initially got my maths wrong.. nevertheless it takes a  lot of simple items to make one legendary and that was the point I was trying to make.

I would think it would be fairly obvious. Each invader has a special set of gear that enhances one aspect of the game process. For example a full set of Lynx gear will increase your defense in all aspects. Saracen is for attack, I think the Royal Guardsman is for hero strength  and so on.

Given that he  apparently wasn't clear enough  in his original question, you have done a very comprehensive job in your post, when he has attempted to clarify matters on what he wanted to know.

However I wonder if he still hasn't been clear enough with his modified  question.

Firstly I would ask him, can you access any or all of them yet? If the answer to any part of it is no, then its probably to early to worry about those that you do not have. 

Lastly, I get the impression that he is asking how to play the game,and there is no problem with asking it, but that comes down to experience and I am not sure there is scope in here to cover every eventuality that might arise , unless you more experienced players can tell me differently and want to divulge it 

However I can think of a few simple solutions to kick things off.

Sometimes  a mixture of equipment is best ,as you have to consider other aspects of your game 

The guardsman equipment if you are attacking invaders

If you send scouts then the hounds, but of course in any action against other players  you may run into defence by that player, so you also have to consider both defence and offense when doing so.

There are specific things the hero should wear , when starting buildings or research or training or doing tasks, or  could wear when yielding ,but also have to consider been attacked whilst doing so

Some of the equipment is geared for specific troops so   what you wear will depend on what you send 

You guys are way over thinking his question:

Use the invaders equipment BEFORE starting an activity. If you  have the full set of gear you want to use for yielding rss, then you put it on before sending your troops out.  Once they are out and on the tile you can take it off and switch to another set.

If you are killing invaders you put the guardsman set on then start killing away.