You can't send mail to yourself, but your bank is shared account wide.
As such you can deposit some gold with one character and then retrieve it with another - similar to how the bank allows you to move items between characters.
Deposited items can be accessed directly when crafting.
Deposited money can't be accessed directly.
Edit:
As of Patch 1.6 ("Update 6"), gold in your bank won't be taken by Guards arresting you due to your previous crimes/bounty.
There's a number of things you can do in ESO as a low-level player in Cyrodiil.
Firstly, you can participate in various forms of PvE content throughout the zone. NPCs are all level 50, but the game does scale your stats to 50 as well, so you'll be able to fare okay. There are a number of dungeons, PvE quests, Skyshards, etc. in Cyrodiil to keep you busy, if you find you're not doing well in PvP right now.
Secondly, you can try to find a group of other players to join. There are usually groups of some sort advertising in Cyrodiil, and having other players to back you up can help even the odds in PvP, or even tip them heavily in your favor.
If you don't want to find a proper group to join, you can also try joining in on a siege. Whether defending or attacking, there will be plenty of players on each side of the conflict, and so plenty of support/buff/heal abilities being thrown around if you need them. The larger number of players also can make it less likely you'll personally be targeted, assuming your side is greater in number.
If you really do want to solo PvP in the zone, there's still a few options. The simplest is to leave for a few levels and come back; at level 15, you gain access to the weapon swap mechanic, and with it you also get a whole second bar of abilities to use. This one mechanic alone can make a huge difference in the performance of some builds. Also, in the early levels, you probably haven't got all your abilities morphed yet; holding off for a few more levels to get some of those upgraded (especially if you're going for morphs on abilities that add healing) can have a big impact.
You should look into improving your ability to sneak. If you're a Bosmer or Khajiit, or using Medium Armor, there are passive abilities in those skills which can help. Even without them, just learning to be aware of your surroundings, learning how close you can get before enemies see you, etc. are very useful in helping you get across Cyrodiil without trouble. A useful tactic is, upon entering sneak mode because there are enemies nearby, wait until you go undetected, then walk away from where you were in a somewhat random direction. Even if an enemy spotted you and heads to where they last saw you, you've since vanished, and it's generally not worth their time to hunt a lone player down.
Lastly, if all of the above isn't enough, you can try switching Campaign. Some of the campaigns can have lop-sided player populations, and if your own alliance is more populous in one campaign, that can translate into an easier experience while you get used to Cyrodiil and ESO PvP in general. You can either switch your Home Campaign, or just enter another one as a guest to get the hang of things. Just look at the little cell-phone-signal-bars icons in the list of campaigns to see how many people from each alliance are in a given campaign.
Best Answer
As of right now (end of May 2015) there aren't any DLCs released so far, since Zenimax Online Studios wanted to release the game on consoles first, then start releasing DLCs (which they've been working on since last year).
So far there's no information available regarding prices, but they've already said, they'd release more information as well as a roadmap soon (i.e. at E3 2015), which will start in about two weeks.
However, since a subscription will also net you crowns to spend (the same amount as if you'd be purchasing the 15 $/€ package once a month), you can also subscribe now and use those bonus crowns later on to buy finished DLC.
The first DLC to be released will be access to the Imperial City, although they haven't stated whether that content would be free for all or indeed be the first DLC (since it's connected to the PvP/AvA endgame).