My question is assume that we know that the degree of some irreducible variety is small does it possible to conclude that there exists polynomial of small degree vanishing on this variety. 


Let us make the question more concrete: 
Let $V\subset A^{2n}$ be an irreducible algebraic variety of dimension $n$ and degree $d$ (say $2^n$).
Let $I \triangleleft \mathbb{C}[x\_1,\ldots, x\_{2n}]$ be an ideal of all polynomials vanishing on $I$. My question is what is the best upper bound on the minimal degree of polynomials in $I$. 


The best upper bound that I know is $2^n$, while I think that it is not the true. 
For example if $V$ is a complete intersection variety then $I$ must have polynomial of degree $2$. 



Minimal degree of polynomial vanishing on the variety of small degree. 
The minimal degree of a polynomial that vanishes on $V$ is the minimal $m$ such that $h\_I(m)\ne 0$, where $h\_I$ denotes the Hilbert function of the variety $V$. Hence, you are interested in upper (and lower?) bounds on the Hilbert function of certain varieties. There are two papers I know that deal with such bounds:


* <http://atlas.mat.ub.es/personals/sombra/publications/hilbert/hilbert5.pdf>
* <http://www.ams.org/journals/spmj/2008-19-06/S1061-0022-08-01031-5/S1061-0022-08-01031-5.pdf>


