Darlene, welcome to the group. Using a single carry-on (plus a personal item) for an extended European visit requires packing disciplines you may not have tried before. Review the packing light theories and practices while you are shopping for a wheeled bag. Most of your existing wardrobe and travel accessories are readily adaptable to going light but you may also be shopping for replacement clothing or specialized items, so give yourself plenty of time to get your stuff together before your big trip. You can take relaxing a multi-day vacation a nearby destination to debug your new bags and packing systems.
Wheeled carry-on bags can range from $50 to $500. Aside from the materials and the quality of the transmission and frame, design differences usually mean a loss of internal space, space you may or may not need depending on your packing abilities. Spinners require a larger frame to accommodate four wheels and, since the external dimensions of all full-size carry-on bags are roughly the same, the frame steals a bit a internal space. Pockets, flaps, expansion abilities, and all those zippers add cost and complexity. You may not need these amenities and they can be more appealing than actually useful; a matter of taste and experience.
I know lots of folks who are delighted with their Rick Steves luggage items and have used them for many years. Of the twenty-eight people on my RS tour of Scotland, I counted fifteen large RS bags and another dozen RS personal items. The RS bags represent good value but there are many other sources and designs. I like my old North Face Rolling Thunder 22-incher ($250-300). It’s basically a no-frills duffle on wheels but it’s built like a tank and I expect it will last decades.
Try to have fun shopping!