Well I live in HK and will be back there on Friday this week after my UK trip so hopefully I can be of some use.
The tourist pass for $300 sounds like good value but the ubiquitous Octopus card (similar to Oyster but miles better) and using the Tung Chung line instead of the Airport express will slash the price of the journey from the Airport and take in more stations too.

. Many locals use the S1 bus from the Airport (from just outside the airport bus station) to Tung Chung MTR then take that train into Kowloon or HK. The fare on the Airport Express to Kowloon is $90 whereas the MTR from Tung Chung is about $16, depending on were you go. Airport Express trains are much nicer but not all that quicker considering unless you are staying adjacent to the MTR station you may require a free shuttle bus which may run only every 20 minutes or so. There are also airport buses, A21, A22 to Kowloon for about $40 or slower 'external' routes E21, E22 etc for about $20 or so. It all depends on your own choice of course, and of course where you are staying.
I don't think the MTR tourist tickets can be topped up. They are valid for three days and then that is it. These are not smart tickets although some ticket changes are happening now so this may change. My own preference would be to buy an Octopus card at the MTR counter in the Airport terminal, I suggest $200 (plus $50 refundable deposit) and then top that up as you go. Any MTR station or 7-Eleven will allow you to top up, $100 - $200 a time should do. Other top up facilities are available but these two are most prevalent and 7-Eleven stores are everywhere.
No idea on buying a suit but anywhere down Nathan Rd, particularly in Tsim Sha Tsui (TST), you will be bombarded with offers to have one made, not to mention copy watches and 'massages' "Massagey ! Massagey ! good price, pretty girl !!!. " etc etc.
Ocean Park is well worth a visit, you can get an admission ticket including bus trip from under the Lippo Centre in Admiralty. If you want to make your own way there and pay on the door then loads of buses stop nearby at the Aberdeen Tunnel Toll Plaza, (bus 171 from Kowloon), the 10 minute walk is signposted. On a weekend / holiday then several divert to go around to Ocean Park bus station which is adjacent to the entrance. Please be aware that there are huge numbers of tourists that visit here so the queues may be lengthy. Go early if possible, 09:30 - 10:00 or so.
The cable car is something I have never done but it is adjacent to Tung Chung MTR. There is also a New Lantao Bus no.23 if you want to experience some of Lantau's scenery from the road. Bus takes about 45 minutes and is a lot less scary since they built a new road over the hill.
Night Market - very touristy and not always good quality. Check out anything you buy there carefully.
10,000 Buddhas is close to Shatin Station. Also somewhere I have never been. Quite a climb up apparently...
Stanley - ahhhh now you are talking. If you want to, from TST there is a 973 bus from Mody Road which will take you there. You MUST go upstairs, right hand side is better for views, front seat preferable. Awesome ride, usually on a newish ADL Enviro 400 although sometimes an older Volvo Olympian. Also a 6, 6X or 260 from Central - differing prices and routes. Stanley is a busy little place, market, beach, restaurants and bars with young
flymo (Ha!) occasionally propping up the bar in the 'Smuggler's Inn.' By occasionally I mean quite often.
Trams are fantastic and unbelievably cheap $2.30 for a single trip. Only along the north shore of HK Island from Kennedy Town to Shau Kei Wan. My suggestion - one tram Kennedy Town to Happy Valley then another Happy Valley to Shau Kei Wan. Total $4.60 for about 2 hours of bone-jarring fun. Marvellous.
Hiking is also good, there are many trails around the place. Some are more demanding than others. Depends on your own ability really but something for everyone.
Getting around is really easy with buses running typically 06:00 - 24:00 7 days a week with some night buses too. Taxis are plentiful and also not too bad price wise. Trams are the cheapest and don't forget the Star Ferry - the best 20p you will ever spend in your life. Also don't forget to do it again at night as the waterfront of HK Island is fantastic when all lit up. It you get to The Peak (Bus 15, minibus 1 or Peak Tram from Garden Rd) then there is a 3 mile or so fairly flat walk around Mt. Austin. Get some good views of the harbour and Kowloon, again different in daytime and at night.
If you are feeling adventurous then the LRT which runs between Tuen Mun, Tin Shui Wai and Yuen Long is worth a trip. Entrance/exit processors on each platform. Quite likely you will be checked.
Make sure you get an Octopus card as it is the only way to pay fares these days. No change is ever given on buses or trams. Octopus cards can also be used as payment for example at vending machines.
one last thing - if you use first class on the MTR (Between Hung Hom and Sheung Shui) then make sure you hit the 1st class processor (on the platform adjacent to the first class carriage) with your Octopus card (Your tourist pass is not valid for this) before you board as you most likely will be checked and maybe fined if you don't. This processor just tells the exit gate to charge you double, i.e. the first class fare. English is fairly widely spoken but not everywhere. Most if not all transportation signs are bi-lingual. Have a ride to an outlying Island, Mui Wo is OK, Cheung Chau also. Octopus welcome for paying.
Good luck !!
