Electrolysis of Water

<...I wanted to ask that whether same amount of gases will be liberated at electrodes if I dip electroded in bucketfull of sea water or directly in sea...>

The quantity of gases released will be about the same, until the stocks of chloride ions in the bucket begin to dwindle; directly in the sea there will be practically no restriction on chloride ions.

<...Consider that I am using same batteries for doing the same. Also how can we enhance Electrolysis of sea water using only different types of electrodes i.e. without adding any additives in it....>

The electrode material makes no difference to the process, other than the caution that the material selected for the + electrode will be critical on account of its ability to withstand corrosion. A platinum electrode would be fine; a magnesium electrode would perish, for example.

As seawater contains anything between oh, say, 30,000 and 45,000 ppm of common salt ions depending upon location, additives will make very little difference.

Increasing the agitation between the electrodes will help speed up the process, which will then take more current than were no agitation applied.

There is an excellent article on electrolysis in Wikipedia.