D&D 5E Character Creation, Help Please
That's an intimidating amount of backstory for a DM to read; I'd be afraid you'd be easily disappointed if it didn't come up a lot but at the same time I wouldn't want to make the campaign all about you and make other players feel left out. Maybe give an abbreviated version up front and let the rest come out piece by piece.
Anyway, as for skills, the outlander background will make you good at hunting, gathering, building shelters, wrestling, climbing, swimming, etc. They combined a lot of skills so no there are only 15 but they each do more. And instead of buying ranks in skills you pick skills you are "proficient" in and get a bonus based on your character level. That would leave you with picking two of the following skills to get that bonus to: Animal Handling, Intimidation, Nature, and Perception.
Perception comes up a lot because it's spot, listen, and search all rolled into one skill. Nature is more of that intellectual knowledge of nature (things you would learn if you went to college for a biology degree in today's world) while survival is the practical stuff. Intimidation is your only good social skill, and you can use your Strength with it instead of Charisma. Animal handling is pretty straightforward.
Starting gear: they give you a few options and really what you chose for a barbarian is up to what you like personally. Some classes get complicated but barbarian is pretty straightforward. The only thing to note is that some smaller melee weapons can be thrown, like javelins and hatchets and daggers.
Starting Attributes: in 5e you cannot start out with an attribute higher than 15 unless you get a bonus from your race. Also now that Barbarian's AC = (10 + Dex modifier + Con modifier + shield bonus to AC) as long as they are not wearing armor. This means that you want Strength, Dexterity, and Constitution to all be high if you're running around without armor. You can use a point buy or a standard array (you assign the following numbers to attributes of your choice: 15, 14, 13, 12, 10, 8). I'd recommend prioritizing your attributes this way: Str>Con>Dex>Wis>Cha>Int. This would give you starting scores of 16, 15, 14, 13, 11, and 9. When you get attribute points to spend you actually get 2 points in 5e, so you can bump up two modifiers at once.
One thing to note: Barbarian's don't get stat increases while raging, instead they get to roll the d20 twice and take the highest roll when making skill and attack rolls that apply your strength modifier. They also take half damage from blunt, piercing, and slashing damage while raging.
There are 4 different subclasses built into the Barbarian class. One is all about dealing damage while raging (path of the Beserker), one is all about defense and strength (bear totem lets you take half damage from every damage type except psychic while you are raging), and they other two make you a ranger while giving you a few cool moves (eagle and wolf totems).
Feats are now an optional rule that since DMs do not allow. Same with multiclassing. And there are now prerequisites the multiclassing rather than XP penalties. In all cases the prerequisites are having certain attributes at 13 or higher. And you have to meet the prerequisites for all classes that you will have. So in order to Multiclass as a barbarian and a bard you would need both your strength and your Charisma to be 13 or higher.