From RH Designs on split-grade printing: "Equal exposures through each filter produces a contrast equivalent to grade 2 (if Ilford Multigrade filters are in use). Thereafter, increasing the hard exposure by a stop will increase contrast by one grade, similarly decreasing it by half a stop will reduce contrast by half a grade."
My measurements using my home-built LED head show the above statement to be true. I can set LED power levels to be any ratio I wish, but which grades do they correspond to? Using Ilford V RC paper, I experimented with Stouffer wedges until my LED test strips perfectly matched those from Ilford filters with a tunsten lamp. The resulting table of power-differences matches the above statement within 0.1 stops for grades 0 to 4. Grades 00 and 5 are exceptions because I light only one LED for them (green for 00 and blue for 5).
For the technically minded, the formula is: grade = 4.1 - (B-G), where B and G are log2(attenuation) of blue and green, meaning they are the number of stops below maximum power of B and G. The formula tells us that for grade 2, blue is 2.1 stops dimmer than green (i.e., B-G=2.1), telling us that tungsten lamps output much less blue than green.
For the OP, I agree with ParkerSmiithPhoto above: Forget about split-grade (and LEDs); first learn the fundamentals of making good negatives and good prints.
I'll add one more: Try to avoid lighting subjects with both sun and shade. Sun+shade results in high contrast negatives that are difficult to print.
Mark Overton