You don't need to buy third-party banks immediately. Roland Zenology (the core library) contains hidden gems. Look for these specific preset names:
Stock presets sound too polished for Pluggnb. You need to "break" them. Here is your checklist for : zenology pluggnb presets
A short decay, high-pitched bell. This is your melody lead. Draw in slow, triplet-based arpeggios. The secret to Pluggnb is using on this preset—bend every root note up 12 cents and back down. You don't need to buy third-party banks immediately