Preordering figures is highly recommended! Scale figures are especially harder to obtain if you don't preorder, depending on its popularity. Also, make sure to put aside some money to ensure your preorders are paid for when you receive the invoice! You can always cancel preorders if you decide you don't want them after all.
Always make sure you are not being overcharged when buying new and preowned figures! This especially goes for prize figures. If you are being charged over twice its original retail price, you may be getting scammed. this doesn't apply if the figure is rare.
Be wary of bootlegs! Amazon, Ebay, and AliExpress are full of bootlegs. If MyFigureCollection does not list the figure, then it's most likely a bootleg. MyFigureCollection also has images of bootlegs, so it's always a good idea to compare images. Also, if a figure is advertised as being from China, then it is most likely a bootleg.