best exterior wood treatment for pine

[carpetbagger]

hi i have just had some new pine driveway gates fitted and would be greatful for any advice you could give me on what to treat them with.i am thinking of using dulux basecoat followed by dulux weathershield stain. i was told in the shop this was the best to use but you never know these days, it is quite expensive (£22.00 for 1 litre of base coat and £22.00 for 1 litre of stain)are there any cheaper or better alternatives that do exacly the same job? thanks in advance john