If you are a PAYE worker between 30-40 you can put 20% of you basic salary into a revenue approved pension and get tax relief at your marginal rate of tax.
They are other factors to look at, like
Size of mortgage
how much putting into SSIA
family situation, ie money put into a pension can not be accessed till at least 55/60
does company have pension scheme
Is difficult to work out future values due to different circumstances like charges and fund performance.
Hope this helps but if you have anymore question just ask.