The typical clothing that all men wore was a tunic, léine, which could vary from being worn knee-length to ankle-length (McClintock, Dunlevy). There are two variants that have been found: sleeved, and sleeveless. The sleeveless one disappears from archaeology after the 6th century (Dunlevy). It was belted, and it was by "girding" up the excess that it could be brought up to the knees, usually for labour or fighting. The neckline could be round, square, triangular or oval (Peter Brown). Leines very often had a hood, which was just part of the garment, like any modern hoodie. You could wear several leines, the bottom-most one acting as an "undershirt".
All men except slaves tended to wear trousers, and even some slaves (if they could afford them, or if their masters gave them). All trousers we have found so far have been "speckled", which you should view as the migration period equivalent of "tartan". There is a theory that the more "speckled" (the more colours and lines) the tartan had, the richer and nobler you were, with the King having 16 colours. But this is just a theory. Your safest bet is a two-colour check pattern, with checkers that are colour 1, colour 2 and half-half. That pattern is from a piece of fabric we actually found, where the colours are black, red and mixed black-red.
The cloak or brat is your straightforward cloak. These have been found unhooded and hooded. At their simplest they were a thick sheet, much like other cloaks of the area. These are described as monochrome, or sometimes with a contrast-coloured fringe (an added piece of wool, not the modern style of fringe). Noblemen or rich men often decorated the hem and collar of their brat with feathers, usually drake or heron feathers (CuChulainn, Poetry). The King or extremely rich people would wear a brat fully covered in feathers. Rich warriors probably would wear feathers on the hem and collar of their brat.
Shoes were simple, usually leather (Lucas). There were many styles, and I can only recommend you try and search for illustrations that have been made for them. A distinctively Irish type is the "ghillie" shoe.
As to patterns, many Irishmen were still Celtic Pagans, and would have had Celtic patterns rather than later period Christian swirls.

Warriors tended to dress slightly differently. Art and archeology show us a lot of men liked to wear their trius (trousers) knee-length, a bit like shorts. They also tended to fight in a simple short-sleeved (elbow length) tunic.

SOURCES: I've named the first few, but I've only used Peter Brown, Dunlevy, Lucas and McClintock, so I didn't bother sourcing the other statements. If you want a specific one cited I'd be glad to!