Eh? So why did you ask how to get to the Mandarin if you wanted to go to Macdonnell Road?

Macdonnell Road is more or less equally uphill from any of the Mandarin, Conrad and Hyatt. Of the three it's closest to the Conrad, and slightly less of a climb from the main lobby. Go out of the main lobby entrance, turn right, cross the road and go into Hong Park, look at the map to follow the paths up the hill the come out of the top of the park on Kennedy Road. Turn right onto Kennedy. Cross over and take Calder Path more or less straight up the hill to Macdonnell and (probably, depending on how low numbers exactly) turn right. I'd allow 20 mins for this if you can walk up hill and climb steps at a reasonable pace. I don't have my contour maps to hand but I guess you're climbing about 300 feet in total.

The only hotel I can think of that is as far up the hill as Macdonnell is the Bishop Lei on Robinson, which would be a 10-15 minute walk to the low numbers of Macdonnell more or less on the flat. But it's a couple of notches down from the Mandarin/Hyatt/Conrad as a hotel.

Alternatively to avoid any uphill walking, from the Conrad you can go down into Admiralty MTR station navigate out to exit B, turn right then right again when you reach street level and there is the bus stop at the start of route 12A which runs about every 10 minutes and gets you to Macdonnell is less than 5 more for HK$4.3, But I guess whatever it is that stops you taking a taxi may also apply to a bus?

On shirts most of the decent places start at about HK$350 for a basic cotton fabric. For less than HK$200 I imagine what you get is very basic indeed.