For FL Studio 10, note that it's a very old version (released 2011). Newer plugins may not be compatible. Upgrading to a more recent FL Studio edition (even the free trial) would give you better plugin support. Nexus Vst Plugin For Fl Studio 10 Free Download
Is there a specific type of sound or music genre you're trying to create? I can suggest free, legal plugins that will work well with your setup. For FL Studio 10, note that it's a
is a proprietary ROMpler (sample-based synthesizer) developed by reFX. It is not free software —it requires a paid license. Any website offering a "free download" of Nexus is almost certainly distributing a pirated/cracked version. For FL Studio 10