Okay, so this is my first guide so bear with me. This guide is not about the optimization of anything but speed, so don't use it if that's not what you're after. But, if you wanna have a little fun and are tired of not being able to reach the other side of the map in under 30 seconds then this is the guide for you.
I'm a decently experienced Soraka player who only enjoys playing her at 100 mph and roaming. I enjoy having this much movement speed because for me, it solves one of Soraka's key weaknesses: how easily she dies when hit with any form of cc.
With the this guide's ms you can easily avoid skill shots, make some crazy getaways and duck in and out of battle when you want to.
Downsides are, your healing only ok, you tend to be at low health a lot due to your healing, you really need to scale and you're very squishy if somehow caught out.
!!! This is a build I came up with recently and am still testing it, so results may vary !!!

So, you've got all this speed now, what are we going to do with it? Why, roam of course! After you grab Wish and your boots, you're free to go where ever without fear of the enemy jungler. With said ms, you should be able to kite anything that comes your way, like Lillia but healing focused. Your Priorities should look something like this:

Staying alive with poke and kiting (Kiting is your best friend)
Providing assistance to your laners and jungler (and watching the mini map for ult opportunities)
Placing Aggressive wards

HOW TO PLAY
The idea of this kit is to provide you(and sometimes your team) with the mobility for easy disengages and escapes. Soraka is very squishy so often you'll be hanging around behind your team healing and occasionally poking with your q for healing and procing Cosmic Drive. Once fully built, when you proc Cosmic Drive you will briefly have over 520 ms, which is very fast. Generally, as long as you play farther back from your team in teamfights, nothing should be able to touch you that you can't outrun.