With armor seals, attack damage and armor pen marks and quints with mr glyphs (optional) if team members only hit lizard once and walk away (I use boots and 3 pots) it can take me down to close to 150 health (I also start on wraiths, which take me to around 390 health first), but I use health pots to get back up to around 400. Without runes, it might be impossible to start red without a hard leash. I play rengar jungle a lot, and can tell you that while he may be the best ganker in the game, his jungle sustain is extremely weak even with the 15% heal. Until you at least get armor seals, it might be best to use junglers like udyr, trundle, ww, or cho to start off with until you get those runes. Or you can start blue and wraiths which will get you to lvl 2, and go for lvl 2 ganks, which if successful will allow you to kill wraiths and take on red as lvl 3 with preferably several health pots left over. Best of luck to you, fellow rengar jungler!