I'm not sure what you did so that the photos transfered via iTunes did not create an album; holding in mind that the photos will only be transfered when you actually sync with iTunes.
That said, I do not recommend using iTunes to sync photos ot the iPad. Albums created this way can only be modified by chaning the source on the computer, and then re-syncing through iTunes. There are other limitations as well.
DropBox is an acceptable way to copy photos ot the iPad's Photos app, if you've already done so. Hold in mind this is a two step process. Once the photos are in DropBox, you still have to copy them to Photos using the DropBox app. Once in Photos, you will have to create the album manually. If the photos all have relativlty close creation dates, it should be easy to select them by groups in the timeline (the Photos tab).
Tap Select at the top right. If there are a few photos to be selected in the group, slelect them individually by tapping the the photo. If most of the photos are to be selected, then use the Select button to the right of the group, then de-select the unwanted photos by tapping on them.
If you want to bypass the internet and send photos directly between your iPad and computer via your local wi-fi network, then I highly recommend PhotoSync by touchbyte GmbH (there are several simlarly named apps). Using their free desktop app you can send photos directly to an album (pre-created) on the iPad.
Note: The desktop app is not strictly required, but it does make things easier.