Zahrah - tbh the above sounds fine. You can use the newborn and up to one month at the same time. The sleeve can just be folded if needed, and it really doesn't matter if slightly long in leg as they don't move at that age!
Then get a couple more in 0-3 as in a few months usually. But 10 sleep suits should be fine.
If baby really gets through all newborn and 0-1 for some reason ie ill with diarrhoea you can just put in a 0-3 whilst you wash. If you find you always run out you can always buy more at the time if needed.
We had:
Newborn :x5 vests, x5 babygrows
0-3: x10 vests,x10 babygrows, x5 cardigans, x5 hats
3-6: x10 vests, x10 babygrows, x5 cardigans, (x5 hats and booties-most fitted from 0-3 range still)
just put 0-3 cardigans etc on from newborn with sleeve turned up. The newborn ones only last 2-3 weeks so seems a waste.
Cardigans easier than jumpers over babygrows if cold. Babygrows until 6 months easier to change, plus cheaper as they outgrow every 2-3 months before 6 months size. After that 6-18 months roughly just soft dungerees/ long sleeve vest/ cardigans/ babygrows still combination.
Oh and if you are thinking of using reusable nappies don't bother with jeans/ leggings/ etc until potty trained, as bulkier bum!