Low Ph bed for growing blue berry

How do i achieve this? Looking to plant out about 300sq/m

Well, firstly, I would say - what is your soil type? Blueberries do best in a low pH soil - anything from 4 - 5.5 depending upon type and cultivar and need free draining soils. Which can be difficult as clay soils or peaty soils frequently hold too much moisture. So, if you have one of these types of soils it'll be a matter of opening up the soil for better drainage. If you happen to have an alkaline soil - especially if it is high - my advice would be to either move or buy your blueberries! It's a hard and time consuming pastime (ie it doesn't happen overnight) changing AND MAINTAINING a pH level.
You would also need to work out carefully your placement of bushes as they need probably 2m between them (They do grow quite big over time) and depending upon the width/length of your plot as to whether you plant them in rows or stagger them in diagonals. Also, birds love them so if you are seriously contemplating this you will need a structure to cage or net them. Nothing is ever as straightforward as it seems to be when you get the lightbulb moment.!

I use pine needles around mine every year & have them planted in a walk in bird proof cage. piquant is absolutely correct in saying that they are not easy to grow & I sometimes wonder if it's worth it, really.
I have found that a variety called "Reka" is my best performer, in a Canterbury climate, so it could well be that others would thrive in your climate whereas they struggle in mine. Maybe you could ask a commercial grower about this?
Good luck

You probably want to invest in a good quality pH meter, not one of those cheap rubbish ones from Mitre10 or Bunnings, we got one for work which was about $180 plus you need to buy different solutions to calibrate it. Worth it though as it is very accurate. Then if you need to lower your soil pH i'd buy a big sack of Aluminium Sulphate. I found some at a place called Clarks (Industrial ? )i think they were called, in Napier. Was about $55 for a 25kg sack which I thought was pretty good compared to the little bags you buy at the above mentioned places. I think you are in Auckland so some of the Rabbiteye varieties of Blueberries would work well for you. We're in Whangarei and this is what we get into the garden centre to sell to our locals.

We grow ours in large pots and mix the soil with peat. They are very rewarding and the main worry is birds, so I have a few metres of cheap tulle netting to wrap around each of them, we only have four, Bird netting doesn’t keep them out.