If the old bike doesn't have clipless pedals you might consider buying a set of those. Of course you would need appropriate shoes, too. That's not dirt cheap* but the pedals and shoes would be transferrable to a new bike if you were to go that route. To me, there are two eras in cycling, BCP and ACP - before clipless pedals and after clipless pedals. And after is sooo much better. If you're going to be riding even a moderately large amount of miles they are really nice to have.
* Like everything else they come in a range of prices. You can spend a whole lot of money if you want to but you can also scrape by on the lower end by shopping for deals at Performance or Nashbar or other online bike stores and maybe by looking for house brands. My first pair of biking shoes (back in the toe clip era) was from Performance and they worked just fine. They wouldn't have wowed any high end roadie, but they were just what I needed to get my foot in the door (pun intended, more or less).