You speak better english then most of the native spanish speakers I find myself queued with, which is a huge help to team communication.
Most supports, including Soraka, will start Faerie charm, wards, potions. Until you level up and can reach the higher masteries on the green tree, this will be 3 wards and two potions, so I'd recommend one each of health and mana.
On your first back, you want to build your faerie charm into a Philosopher's stone to start on your passive gold generation. You should also pick up as many additional wards as you can. Try to avoid backing until you can afford the Philo stone and at least one ward, if at all possible.
After that, you'll want to go for boots or a second gold per ten item. You have a choice between Kage's pick, which will increase your AP and make your healing and other spell effects more powerful, and Heart of gold, which increases your HP. I usually go for Heart of gold simply because Soraka is a very squishy champion, and the extra HP prevents me from being bursted down too easily.
Usually I'll pick up a Ruby crystal(or Amplifying tome, for the pick) if I can afford it, or boots if I can't, or if I really need another ward to take back to lane.
Once I have both gold per ten items and basic boots, I make sure to maximize my wards picked up every trip back before I focus on building anymore, unless I can skip one or two to get my next item and still come back to lane with 3+ wards.
I'll usually build Ionian boots for the CDR, which I find most useful on Soraka, but the defensive boots, Ninja tabi and Mercury treads, can also be useful, and I know of some supports that build Mobility boots, especially if they plan to pick up an oracle and clear wards. Since Soraka is capable of influencing fights around the map with her ultimate, and so doesn't need to roam quickly, and is usually too squishy to hold an oracle well, I don't personally use the Mobility boots. However, it can still be worthwhile to pickup an oracle in some situations - just be careful with it.
After that, you'll want to build Aura items that help your teammates. I almost always pick up Aegis of the Legion, no matter which support I'm playing. My second aura will often be Soul shroud; however, Zeke's on a heavy AD team, or Will of the Ancients or Abyssal sceptre on AP heavy teams(as long as the APs aren't using those items, which many do build), can be good purchases as well.
After my second aura I upgrade my Philo stone to Shurelya's reverie, although many supports will upgrade it alot earlier. I like to keep the passive gold coming in as long as possible, but if you feel your team will benefit from the Shurelya activate, by all means take it earlier.
Finally, upgrade the Heart of gold to a Randuin's or Locket, depending on the situation. If you have a Kage's pick, either upgrade it to DFG or Morello's, or sell it for another AP item. However, it will be very rare that you make it to a full build on a support. If you do, start buying red and blue elixirs.
Keep in mind that during all of this, you'll want to have at least a full stack of 5 wards on you whenever possible. This means you don't build an item like Randuin's by filling your last open inventory space with the Warden's mail - you need that space for wards, and you should always have them available.
I mentioned Oracle's elixir briefly above - as a support, you should be sharing the purchase of new Oracle's(when the old one is removed by death) with the tanks on your team - usually the jungler, but occasionally the top laner. This lets you spread the cost out, so one person isn't constantly buying the new one, slowing down their build, and dying as a result.
At your level, your opponents probably won't be warding much, if at all, so you may not have to worry about the Oracle's for a long time. You should still be warding for your team, of course - it will give them a significant advantage to have vision of the other team.
Hope this helps - good luck.
Edit: Sorry, I see you also mentioned which skills to level. I usually start Infuse, since it has the dual use of restoring mana to an ally or silencing an enemy. I take heal second, and starcall last, simply because I rarely need to deal AoE damage as a support - using Starcall in lane will often cause your lane partner to have more trouble last hitting. Sometimes, I actually leave starcall for later, and just alternate Infuse and Heal for a few levels. Obviously take your ultimate at levels 6, 11, and 16, and max Infuse or Heal first(depending on which you find yourself using more often in lane), and Starcall last.