With elliot waves is the purpose to trade each wave or wait til 5th and trade the reversal? do you have risk behind the waves?
According to me, best wave to trade is wave 3 as it's supposed to be the most powerful (at least it shouldn't be the weakest) of all.
As of risk, in the case of trading wave 3, entry is at break of wave 1 top(bottom for downtrend) and sl below what is identified as start of wave 3.
Since wave 3 is normaly not the smallesst wave, you can set first tp at 100% of wave 1 (starting from beginning of wave 3, not from entry point). Depending on the depth of wave 2, this specific trade (entry at break of wave 1, tp at 100% of wave 1) may not be interesting in terms of R/R ratio.
I guess others may have another view on this specific question.