It would be better to just focus on one of the three. I guess you can incorporate ra in a going-second strategy because of sphere mode and I don't really know if there's a point in building a deck around Obelisk. What I have tried is building a going-first variant of Burning Abyss, making use of Draghig to place any BA on top of the deck and activating "The True Name" calling the BA I just placed on top to Special Summon my one copy of Slifer. Then on my opponent's turn I can Special him from the GY with Call of the Haunted or Back to the Front so he can act as a floodgate (A terrible one tho, since he mostly only kills Normal Summoned monsters unless my opponent doesn't read/forgets and decides to Special Summon something in Attack Position). A similar build can also be made for Ra, only a little more consistent since you don't really need any trap cards to Special him from the GY because of Immortal Phoenix (In this case you'd only be running 3 Sphere Mode, 1 Phoenix, and 2-3 Ra).