Enhancing from 21 to 30 is just the same pattern as earlier levels, just + 2 more Rs per skill level up.

So basically:

20 -> 21 : 2 slv14 SRs + 12 Rs
21 -> 22 : 3 slv14 SRs
22 -> 23 : 3 slv14 SRs + 2 Rs
... etc.
Maybe a slv 2 SSR fodder at the end (29 -> 30) for the most possible effect.


As an aside, while I certainly wouldn't call a 51k team "weak", as an old timer myself (started in the first week I think) who has been somewhat neglecting my light grid, I can't help but think that 51k does seem rather low, especially if you're going to be maining an element. For comparison purposes, my Light team is my 3rd team, using a full event weapon grid (aside from soul weapon ofc) and 2 SRs (why it's my 3rd team), and it's rated at 57k with 145 assault, 63 defender. Even the horror that is the fire grid (by far my worst) is still rated at 55k. I can only think it's because you've put no effort into raising the bonuses (+99s) on your weapons/eidolons, and while they might seem like a very small bonus at first, they can quickly add up to a lot of atk, which is especially important when your grid is strong (since it multiplies the effect). If you're going to main an element you really need to put in that effort, because you're going to need everything you can get to overcome the benefits of elemental advantage.