I'd say just buy whatever it is that you like. Granted, there are some games that are ridiculously priced (like a legit Sapphire) but for the most part I just look at for sale threads and ebay and see if I sell anything I like for the price I'm willing to pay.
However, you buying Dracula X as one of your first games is a HUGE mistake. HUGE.
My reasoning: I did the same thing. I bought a Duo a few years back specifically for Dracula X (PCE emulators sucked balls back then.) First I got the Duo with Gate of Thunder, then I picked up Lords of Thunder and a few hucards. Finally I bit the bullet and bought Dracula X, I paid $130 or so. It is fantastic, I love it dearly and it's the only expensive game I own that was worth every penny. Now the bad part-I was spoiled! Very few other games measured up to Dracula X, and the fact is I didn't get any more games for many years. I finally jumped back in when I started getting into shooters.
Luckily the PC Engine (the Japanese model in particular) is a great collectors system if you aren't obsessive compulsive. With the exception of a few high end titles, every good game is affordable, if not downright cheap. It makes me happy after having a love affair with the Neo Geo last year (ouch.)