Which would be the best option I am currently NZ Silver Expires in a month But I will do another Business class flight in April from BNE to LAX via AKL with NZ, Then Economy

Which would be the best option

I am currently NZ Silver Expires in a month

But I will do another Business class flight in April from BNE to LAX via AKL with NZ, Then Economy back to Australia

Should I pool my Status Credits from this Flight in to the NZ FFQ or Should I try and aim for gold with Aegean Mile and Bonus

http://www.ausbt.com.au/how-to-get-star-alliance-gold-frequent-flyer-status-with-one-flight

I am not sure if these flights to the U.S will get me gold and I am not quite sure how to find out

Follow these steps:

1) Identify the number of miles for all sectors flown (Tip: Google "milecalc" for a good link to use)

2) Identify the booking inventory of the flight 

3) Under "Programme Description" menu, select "Earn Miles" on the Aegean website (Tip: Google "Miles and Bonus Aegean")

4) Identify the table for Air NZ - That table will provide you with the appropriate multiplier for miles depending on booking inventory. This will give you your Aegean Tier Miles.

5) Sum the results and if the total is 20,000 Tier Miles and above, you will hit Gold.

Ok...

Interesting on the Miles and Bonus website it says you will need to get 16,000 Miles

"Once you have collected 16,000 miles within one year from the date which you qualified to the Blue status, you will receive the Gold Card."

According to a Miles and Bonus Calc I should earn 17.463 Miles

Which should cut it for Gold

You will need 16,000 miles from Aegean Blue status. As per A3 T&C:

"B. GOLD Card: 

Members who hold a BLUE Card and who have earned at least 16,000 Tier Miles within twelve (12) consecutive months from their first miles-accruing flight on the previous tier will receive the GOLD Card."

"A. BLUE Card: 

Basic Members, who have accumulated at least 4,000 Tier Miles within twelve consecutive (12) months from the date of their first valid flight that registered miles, will receive the plastic BLUE Card."

4,000 + 16,000 = 20,000

Aegean Airlines Miles&Bonus Calculator

Assuming 17,463 is accurate (sorry I'm not following the documentation), you will need a further 2,537 Tier Miles to hit Gold on Aegean. 

If most of your flights are around NZ and Australia why consider joing Virgin Velocity and obtain gold status.  It is easy to obtain *A gold status with Aegean FFP but the difficulty is redeemptin of the miles.