You can easily calculate that by yourself if you put down a list of SP consumption per skill per 20 seconds. If you want to live without any SP potions, the amount of basic + SPR-induced SP recovery rate must be equal or larger to that number.
You won’t like the number, though.
If you have wasted points into leveling Smite to 15 e.g., you will need a lot of SPR to cover that SP-loss. Judging from my level 279 Chaplain-Druid who’s nearly full SPR, I can regenerate around 1090 SP every 20 seconds with 284 points of SPR.
Let’s give you the credit of having Zeymyna at level 6 (Divine Might), resulting in 28 SP reduction per cast, and 15 seconds recovery time. To recover Smite at level 15 + Conviction level 5 combo alone, you’d need to recover 31 (1/3 Zeymyna statue 6) + 69 (Conviction 5) + 2x 150 (Smite 15) = 400 SP every 15 seconds.
My Kabbalist at level 321 has 288 SP recovery base without any equipment, so that’s ± 270 SP if we take off the base 7 SPR. Let’s conclude that you get around 0,85 SP recovery rate per level, which leads to ~296 base SP recovery at max level. This means you’d have to cover at the very least 300-500 more SP recovery through SPR, the best estimate without having to calculate everything would be around 600 SP (but this depends on all skills you use and their levels, all attributes you have active and what else), which is somewhere around 235+ SPR.
But that’s just a rough estimate, you’d have to do the math yourselves as I don’t have your gear,skillbuild and skillrotation…