A Golf ball can cost as little as £1 or $1 but as much as £3.50 or $4.50. Depends which brand you get.
(Prices are not converted, they reflect the price differences between sales prices in UK and US)
A inexpensive idea is to find Golf themed novelty gifts. (mugs, t-shirts socks) you may even find that you can buy a Gift certificate for the local golf range.
I am including a couple of sites that can help you with your golf league shirts www.skylineshirts.com/Custom_Golf_Shirt this site is on custom golf shirts check this one out. This site is about logos of golf shirts www.corpgolfusa.com/
the store in Illinois that personalizes golf t-shirts is called Golf Apparel, it is a well owned store and many people go to it for there shirts and supplies.
cheap, inexpensive
Nike make their own shirts.
Lacoste does offer golf shirts. These are the ones offered directly on their website: http://shop.lacoste.com/Golf-Men-Products/b/2581289011
expensive.
Golf shirts are always a good gift.
Expensive: many money is needed. Inexpensive: a low amount of money is needed.
Ashworth golf shirts can be bought directly from the Ashworth Inc. website. One can also buy the Ashworth gold shirts from eBay or Amazon for a reasonable price.
Expensive
Shirtcamp offers golf shirts in bulk lots of 500. Also check out bulklotshirts and wholesaleclothingsource. Threadairgroup also offers low prices on shirts.