"
should I go to my bank and get bills from there exchange section or...should I go on eBay etc and get lots of world coins and bills"
- I would tap into whatever source works for you while trying to keep costs down & with one principle in mind & that is "quality over quantity."
- It's great you have a goal in mind (Commonwealth currency) so the next thing you may want to focus on is which denominations (while maintaining high UNC like grades). It will become more and more difficult to source nice crisp older series when sourcing notes from banks/exchange houses. I think you'll find some eBay sellers fairly inexpensive if you just keep searching. Some sellers offer extensive listings with either
True
Auction
style
Listings (
TAsL) or
Buy
it
Now (
BIN). I use
BIN for inexpensive fillers & TAsL for the tougher more expensive
TPG (
Third
Party
Graded) banknotes. Some sellers offer significant discounts on lots of 2 or more (which may pay down the road if you're open to swapping). That would be the odd occasion when buying extra might prove beneficial. I have often saved (in my Watch list) certain BIN listings & have had sellers offer further discounts (which I usually snap up). I cover some of these topics on
my website Good luck!