I've played a few with Ra, I played more recently because of this Reward, but I find it simple and easy to use specially at the begging of the game since you will farm gold easily but you are a little vulnerable because of you low health even with a good build.
Ra has a nice range of its auto attack, and for some skills too, but you must have a good aim since you will be attacking from long distance, and the other attention that you must have is to be aware when you character get faster because its passive, Speed of Light, that will make you faster for a few seconds every time you use a skill!
Now the Celestial Beam will be the more useful skill for farming since it will create a beam of light that deal a real good damage and do this in a line of minions will help you to get gold faster but the enemy god will avoid it without much difficult, use wisely
The Divine Light for me is the worse skill for me, maybe it is more useful when I get better, but it will make you to go in direction of the enemy, it deals a nice damage but it won't stop the enemy to attack you while you waiting the attack to explode, since this attack will make an circle that will slow the enemy and will explode in the end.
The Solar Blessing, some time looks like more a skill for a support, since it will be very useful to heal your team, but it also deals damage in the enemies. It will create and and fix circle on the ground, the enemy inside will suffer some damage and the allies will heal.
You ultra Searing Pain, is like the Celestial Beam on steroids, and make a beam in the direction where you are aiming and will deal a good amount of damage and the best part is that one is hard to avoid since it will activate very fast, just practice your aim and will have no problems.
And how I said Ra has a great attack but some skill are a little hard to use, and some works so much well in team fight but this is a problem in the start and middle of the fame since this is a mid lane god, and you will be fight alone most of the time, so remember this before go with so much confidence with him in Conquest map!