Still quite new to Skyrim having never played Oblivion etc so Im having a bit of trouble figuring out the Factions. Now im a fan of the Fallout series so i assume its a similar idea.

Just wondering if anybody could tell me, is there benefits/negatives to joining these factions ? and can you join more that one etc ?

im sure ill find out the more i play the game (currently about 14 hours in) but just looking for some rough guidance just now.

Cheers.

You can join as many factions as you want. Some make a character type for each faction or group of factions. Some play them all as one character.

Most quest lines are kind of short. If you seek out the Radiant Quests that each faction has, you can extend out the experience. You just have to ignore the sense of urgency in the factions that lead you to the next stage of the main faction quest. Some factions have unique armor or weapons or other treats, so there are rewards.

The four main faction: Companions, College of Winterhold, Thieves Guild and Drak Brotherhood are all designed to unrelated, making it possible for those who want to "complete" the main factions on one character. There is no real downside in joining any.
As for the Civil War factions: The Imperial Legion and the Stormcloaks, they are mutually exclusive and will affect who controls the different holds in the land.

this game is very much centered on you, hairybeaver, as a roleplayer.

the main factions are good (stormcloaks) and evil (aldmeri)
neutral is the imperial.

since, the game is called skyrim, i chose a nord (which i've never done first in any game) loyalist (stormcloaks) that specializes in 1-h/block/light (major) and archery/speech (minor) and smith.

go slow, don't make your map circumferance large and work your defense/offense, and, not your extras.

If you are playing to complete everything, and 'beat the game', go ahead and join all of them. If you are role playing, only join those that make sense for that character. Especially for mages, there is a lot of stuff in the College of Winterhold you won't get elsewhere, but they all offer unique equipment.

The Factions within TES games are designed to be played how you want to play them. As is suggested above you can access all guilds with one character with no penalties.

Each of the Factions are focused on, but not exclusive to, one of the playstyles,

Companions focuses on melee/armored Characters
College focuses on Magic users
Thieves guild focuses on Sneaks
Dark Brotherhood - focuses on any of the above who love to kill.

Each has their own storyline and quests, the benefits are things like Faction HQ's that you can access Beds, storage and Trainers in the associated skills, there are also radiant quests givers within the factions and some can be repeated over for more gold.

Try them all and see which you like best you can always make a new character to refine how you want to play.

Fixed.