I have a 3Vpp wave that I would like to amplify to 50-100Vpp. I was using a transformer but after a few tries, i got to think that this was nowhere near being the right way. Can anyone offer some advice?
Why don't you just try using an op-amp? Bias the op-amp according to the specifications on the data sheet. Then just use two resistors to obtain a gain between 50-100Vpp. Try looking up inverting/noninverting op-amp configurations for help.
You say nothing about things like, DC component, linearity, output impeadence, frequency.
Also, it's not clear if you mean that final output can be anywhere from 50-100VPP or if you need it to be variable [from 50VPP to 100VPP].
But if it's merely a low frequency, Voltage Amp that you require [i.e. only small amount of drive current, required] and if you can get by with "reasonable" linearity [i.e. mild distortion not an issue],
with no DC component to deal with, then I suggest a 2-stage approach. First stage op-amp to get the signal to around 27VPP, then a common emitter class-A final stage.