Plasma (quasi)neutrality There are (in an introductory level) three parameter to consider a plasma to be quasineutral or neutral
The time between collisions per oscillation must be greater than one
$\omega_p\tau_c >> 1$
The number of particles in a Debye sphere must be also greater than one
$N=n_o\lambda_D >> 1$
and the Debye length must be much smaller than the length of what we're studying
$L>>\lambda_D$
but how big are those parameters? I mean $10^{3}$, $10^{10}$, $10^{100}$ ??
 A: To answer your question, let's first look at the Debye length $\lambda_D$: this is the distance over which the electric field of a test charge in a plasma is screened by the plasma (or, to be more precise, where the field of the test charge drops to $1/e$). 
It scales as $\lambda_D \propto \sqrt{T_e/n_e}$ and depending on electron temperature $T_e$ and electron density $n_e$ it varies over orders of magnitude, as said by @honeste_vivere.
The number of particles in the Debye sphere $N_D$ scales as $N_D\propto n \lambda_D^3$ and, again, it can vary over orders of magnitude.
The last criterion, which you listed as first criterion, is a bit more complicated as it involves two parameters: the electron plasma frequency $\omega_{pe}$ and the collision time $\tau$. The first one scales as $\omega_{pe}\propto\sqrt{n_e}$. The latter depends on which type of collisions we are looking at (the degree of ionization of the plasma can also vary over a few orders of magnitude), electrons with neutrals or electrons with electrons. The first one depends on the type of gas and the neutral gas pressure (summarized in the collisional cross section).
The following table might give you an idea about the parameter space that is covered (and that it indeed spans several orders of magnitude).
\begin{array}{c|ccccc}
\hline
\mbox{Plasma}& T_e \mbox{ in eV}  & n_e \mbox{ in}\ \mathrm{m}^{-3} & \lambda_D \mbox{ in}\ \mathrm{m}  & N_D & \omega_{pe} \mbox{ in}\ \mathrm{s}^{-1}\\ \hline
\mbox{tokamak}             & 10^4 & 10^{20} & 10^{-4} & 10^{8} & 5\cdot10^{11}\\ 
\mbox{solar core}          & 10^3 & 10^{30} & 10^{-10} & 10^{2} & 5\cdot10^{16}\\ 
\mbox{gas discharge}       & 1    & 10^{16} & 10^{-4} & 10^{4} & 5\cdot10^{9}\\
\mbox{ionosphere}          & 0.1  & 10^{12} & 10^{-3} & 10^{5} & 5\cdot10^{7}\\ 
\mbox{interstellar medium} & 1    & 10^{6}  & 10      & 10^{9} & 5\cdot10^{4}\\ \hline
\end{array}
