Work experience Q

I just want to clear my mind on this so i thought i should ask.

How much work experience in general is needed to safely get an offer lets say for uni? And how much would be enough to get offers for history in uni , im aiming for Russel group ones ?

Iv'e currently ended 3 months worth of History (TA) work experience and over weekends about 4 years (i know it sounds weird) worth of administrative/physical work at a local carpet shop. I've got alot more littler things that are recent.

Thanks