I've rarely used the "paid for" stuff – it's main advantage seems to be real-time protection though you can get that for free with Windows Defender (there's a whole brigade that will argue that it's no good of course). Windows 10 firewall is perfectly good and no need to pay for one.
One of the best programs for getting rid of already installed bad stuff is Malwarebytes – the non-real-time version is completely free and with its associated subprograms is very effective. The real-time version is not too expensive if you feel you need it.
In my experience a lot of malware gets onto the PC (1) with downloads from sites offering legitimate "try and buy" or free software. The way round this is to download from the original vendors site. The other way to get malware onto your PC is to (2) click on something that you're not completely sure is safe. Avoiding both 1 & 2 will go a long way to keeping you safe – I very rarely, if ever, get a problem.
It's always worth looking to see what security services your Internet provider provides. There may be some free or low-cost options.
Whatever security programs you employ will have vulnerabilities and these will vary from time to time. There are plenty of serious reviews on the net and if you can maintain the will to live while ploughing through them, you will probably come to the conclusion that they're all a bit of a muchness. If I were cynical (and I often am) I would regard the paid-for sellers as a bit like vendors selling trading solutions. It's in their interest to worry you into buying the latest updated fancy interfaced version. Many years ago I used to use AVG free – it was simple, effective and just worked. But they kept "improving" it to the stage where it became over-complicated and began slowing down the running of the PC. So I dumped it. It helps if you are savvy with the workings of your PC – try looking at Windows task manager to get some idea, if you're not already familiar.
Another useful piece of software is a decent uninstaller. A lot of software even when uninstalled leaves stuff behind and sometimes it's not just junk. Best free uninstaller I've come across is Revo UnInstaller which will first of all run the "to be got rid of" program's own uninstall routine and then do its own deep search of all remaining stuff. An excellent free program which will surprise you with what it finds after you think software has been uninstalled.
Another source of dodgy software and download links is your email. Just make sure that everything not from trusted senders goes into your junk folder where its links and ability to do you harm will be disabled. This is dead easy with most email client programs.
Do also make sure that your router is correctly set up – this can be a first line of defence.
If it comes to the worst and you suspect you have something nasty infecting your computer then take action to disconnect it from the Internet – pull out the Internet cable or as is more likely, disable the Wi-Fi connection. Then run your antivirus sweep. If the AV software needs updating, download it from an alternative safe source.
If it comes to the worst and your computer is completely trashed by a virus and appears to be irrecoverable then you will have to rely upon your backups. (You do regularly backup your data don't you?
) In addition to that you also need your reinstall disc or a backup image of the operating system. Many commercial PCs have a special hidden partition on the hard drive which enables you to restore factory state to the main hard drive area. (Works well until the hard drive itself fails, in which case you are fairly well stuffed if you haven't got any kind of backup - though you can sometimes download the image from the manufacturers website).
As a trader it's always sensible to have an alternative means of access to your account (phone/tablet/laptop et cetera) should your main PC fail.
My last suggestion if you are non-PC savvy or don't have the time or inclination to become so: get your PC from the local tech-computer shop (not PC World!) who will, if they're worth their salt, custom build a PC for you. They will then know of its innards and be able to do any restoration work for you. Although I build my own PCs just for the fun of it, it doesn't actually save very much money compared to going to my local PC guys. They even have a service whereby they will remote into your computer from the workshop and fix any software problems without you having to take the kit in/them visiting you. I think they charge £6 monthly and I don't think that's bad value compared to brokerage fees – especially if you're not a computer geek.
Hope that's of some use. (Just reread your original question so apologies if this has rambled on a bit more than you asked) Just be careful what you click on!
PS – just read the excellent suggestions from f2calv at #3
