I'm a sage healer and it can be hard at first without some decent gear but it's also important that you are doing some basic things when healing to make your job easier. Below I will give some quick but I think good advice to get you started.
Gear wise you should aim for getting the Rakata implants and earpieces from the belsavis, ilum and corellia dailies. Get your Biochem up to 400 so you can learn and create stims especially your Rakata Resolve Stim
which will boost your power and willpower. Create your matrix cube
(relic) which will boost most major stats that you need, guide here
. Also collect all the willpower and endurance datacrons and it will boost your stats considerably where you can find these datacrons can be found here
. And a quick search on youtube is where you can watch videos on how to get to them.
Healing builds are vital to how efficient of a healer you are, I'm using this build
right now and that or something similar will serve you well.
Stats are important to every class but the ones important to a sage/sorc healer are as follows:
Power --> Willpower --> Crit --> Alacrity --> Endurance
This is the order you want to stack your stats once you reach around 30-35% crit because after that it suffers from diminishing returns. Power gives you more bang for buck than willpower, especially when using Healing Trance. But willpower is also very important too, so a good amount of that is very desired.
There is no rotation as a healer, it's mostly about feel and very situational however there are some basic things you should be doing to make your life a lot easier. The first thing is the UI setup, don't stick with the default party frames instead go for something like this
, it will make your life a whole lot easier (even better now with UI editor in 1.2).
As for healing always pop Rejuvenate (on tank if possible) when off cooldown as will grant Conveyance which will boost most of your main healing spells. Healing Trance should be used often after a Rejuv as it's your most force efficient ability plus a crit will grant you Resplendence which will make next use of Noble Sacrifice activate without degenerating force. Use Deliverance as your main healing spell, hardly ever use Benevolence because even though it's fast it's very force in-efficient for the amount it heals... only use it in emergency situations. Pop Force Shield on the tank (or in some cases the whole party) before a fight as it can buy you a lot of time and take some healing stress off you. In cases where the party are grouped up or lots of mobs are around use Salvation, it's a great AoE heal. And a good way to get your health back after use of Noble Sacrifice is to use Salvation on yourself (or stand near it) and use Noble Sacrifice 2-3 times, this is great if you can also do it when you have the Resplendence buff.
Hope this info helps!!