Marbella as home base/help with itinerary & more

Marbella is not the most convenient place to base for day trips because it doesn’t have a train station. You would need buses and then switch to trains. Your resort may not be in a location where it makes it easy to catch a bus. For Malaga, you could easily get a taxi but I’m not sure if a taxi would take you as far as Córdoba etc.

I haven’t been to Gibraltar but nobody who goes there seems to like it much. It’s definitely not a priority with so many better places to see.

Marbella is also expensive.

Do not miss Seville, it is the gem of the south.

Marbella is also expensive.

That all depends on where you stay, where you eat, where you drink, where you shop ad nauseum.

I've been staying near to Marbella for a number of years and regularly visit the town when there and find it no more expensive than other areas in Spain. It does have resorts, hotels, bars, restaurants etc catering for a higher end clientele but there are plenty of establishments aimed at the more mainstream market.

My advice would be to rent a car. Driving in Spain is not really much different than driving in the busier parts of the US. It'll be more convenient, you won't be tied to public transportation timetables and it'll be a lot cheaper than hiring a driver.

Marbella is absolutely gorgeous, and I'm sure you'll love it. I'll echo the suggestion to get a rental car.

As for side trips, I'd advise you to not miss Granada and the Alhambra. Be sure to get Alhambra tickets well in advance. Ronda and Málaga I also would urge you to visit. Finally, Córdoba: I personally found little to recommend the place, and I found the bullfighting vibe that permeates the city to be off-putting. Others disagree with me.

Sevilla and Madrid are both marvelous cities. Have a great time!

We are doing a similar trip this summer. Flying into Madrid-taking train to Malaga. Picking up a car and we will be based at a resort in Marbella for 5 nights. We are going to the Alhambra one day (we have tickets) and will look around Granada that day as well. We also might do Gibraltar, Rhonda and a water park (we have young teens). Then we are driving to Portugal for 3 nights-then driving to Seville where we will spend a few nights. We will return the car there and take the train to Madrid-and spend a few days there. We are stopping at Cordoba on the way to Seville-will spend most of a day there.
I think being based in Marbella means you pretty much have to have a car if you want to see other places. I think our resort is even 25 minutes away from the town of Marbella itself.

Last September, we visited all of the places you mention…except Marbella. I would highly recommend renting a car (get an International Drivers License) and prioritizing Cordoba and the El Caminito del Rey. Driving in Spain is easy except in the old city centers, especially Granada. The Alhambra is awesome but Granada was extremely crowded and driving there is impossible. For us, the Mezquita was more impressive and Cordoba a lovelier town. We found Malaga to be beautiful, relaxed, welcoming, and delicious. Going to Gibraltor, and the top of the rock, was an experience but not one I would choose to repeat. Ronda was packed with tourists and unwelcoming. So, for what is worth, consider visiting Malaga and Cordoba and hiking the El Caminito del Rey.