are you close? 30 is a somewhat high requirement, if I didn't committed to the blitz battle I would struggle as well.
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now I really want the 5 "more" legends. and the 5 gems each side (under 4k), to compensate the 6 (maybe) gems already spent on this.
I don't know, when I think I have most legends already is kinda bad (out of 50, I have 32 already) , but still... its possible... it can be 5 chances.
the ones I want the most are shirahoshi (normal chances), marco (also nice chances), v2 ray (from the pool on reddit, on the lower side), robin (another rare one), maybe franky? or any of the strong (v2 akainu, v2 aokiji, v2 doffy, v2 fuji, neko...) or usefull (legend usopp, magellan, even buggy) . other than that I would take anyone new (like v1 fuji or v1 lucci) , or a good dupe (judge, or maybe someone strong to keep unevolved for rankings like "kevin")
am I dreaming too high?
I just reached it now(was around 13 when I posted it, farmed the 15-Stamina).
I'd say that I was too busy with work these days, but to be honest, the real cause is Spiderman XD
About your question, I think with 5 legend pulls you have decent chances to get at least a new/desired unit, so go for it!
I want to save for V2 G4, but I end up falling for every discounted and pre-TM sugo. At least I haven't needed to buy gems for those.
Urp, now that I think about it, I'm totally going to miss the next TM. Kizaru seemed nice, but I can always wait for the rerun