Just because you plan to dive wrecks in the future, should not rule out a good dive computer purchase now. It just means you should think about a quality dive computer, with a gauge mode feature, so that you can use it in the future when you do dive wrecks.
If you get a Suunto Vyper dive computer, you can use it for all kinds of diving, and you will be glad you have it, because it records all the details of your dive, so that you can read it back afterwards in the PROFILE feature.
If you are diving to a wreck, you will probably stay at one given depth. So whether you use a bottom timer or a dive computer does not matter much.
But in the meantime, while you are diving NDL open water dives, a dive computer is quite nice, to keep track of your remaining NDL time. A nitrox dive computer is expecially nice, since you may be doing repetitive diving, and nitrox lends itself well to numerous repetitive dives.
If you are penitrating the wreck, or staying down longer than NDL, or going deeper, then you will have multiple gasses with you and will be deco diving. In that case your Suunto will still work well, however it will be in GAUGE mode, where there is no NDL model.
For tech diving, you would normally use some kind of depth/time gauge, and possibly some type of backup gauge (not all agencies require a backup gauge).
So a dive computer is a good investment. You just need to make sure you get a good one, rather than a cheap one.