Well, if you really are totally new to boating you have got a steep learning curve coming up! Don't give up, it is really worth the effort
New or secondhand I think that you need to think carefully about the intended use you are going to put the boat to. My first boat was new, but I had spent years with diving club SIBs and RIBS. I wanted the re-assurance of reliability, which is not to say that you will not get a reliable secondhand boat.
Are you going to be going to sea with other boats, or are you anticipating being a loner? If a loner, could you be out after dark? If so you are already needing nav lights and VHF of some description (plus other safety gear which will not necessarily be fixed to the boat!). This is just one example that comes readily to mind. Write up what you want to do, and then list what the boat will need to have to enable to do these activities safely.
Finally, I also do much of my boating on the Solent, it has an unusual characteristic called the Solent Chop. Usually it is impossible to 'drive' it to minimise the abuse the boat and crew take, so for my money a 'soft' riding boat is worthwhile. Good luck, post any questions that you have, I am sure that you will get many answers.