I don’t know, but this is bothering: Every pattern has a different needle size. What do I do?
Buy them all!
:rofling:
Many of us have interchangeable needles to solve that problem. There is a thread at the top of the forum about them. If can’t afford them or don’t want to then the only solution is to buy them as you need them. 
Here are some links to two threads about needles.
Thread One
Thread Two
I bought needles virtually every pay day for the 2 yrs I’ve been knitting until I got all of the sizes that I wanted. Then, my husband surprised me with a set of Denises one day…I continued to collect needles…then I got the KnitPick Options set…I will continue to collect needles…it’s a sickness…part of my knitting addiction 
:rofling: :roflhard: :rofling: And there’s no help for it :rofling: :roflhard: :rofling:
Hi Glucose
I know the feeling - fortunately, there’s always charity shops here that sell second-hand needles and my particular favourite are old Aero ones. The points are extremely well-tapered (like the green ones on Amy’s videos).
If you don’t want to keep paying full price, perhaps checkout your e.bay site - where you can pick up some real bargains.
Good Hunting!
Best Wishes
Limey
I had lots of different needles and still needed more
with each pattern I wanted to make. Then I got some extra $$$ and I treated myself to the Denise Interchangeable set and
I LOVE them. I haven’t had to buy any more sizes yet. They are wonderful to work with. 