"Ni siquiera" is used a lot in Spain. You can use it in the sentence "Ni siquiera yo lo haría" that is translated how "Even I wouldn't do it". You have to remember that the negatives are different in English and Spanish. "Ni siquiera" is to say that something wouldn't happen even if it is very easy to occur. You can use "Siquiera" in the same way but is more antique. Other manners to say the same: "Ni siquiera yo lo haría", "Ni yo lo haría", "Siquiera yo lo haría", "Incluso yo NO lo haría (this sentence is in positive, so you can put NO if you want the same translation). I hope tha this could help you, and if you want we can talk more. Ps: Sorry if I wrote something wrong, I am trying to improve my English skills.