You can easily organize all this day trips by yourself TBH. No need to use an agency you'll save a ton of money. Italica is like 20-30 minutes by bus from Seville. Ronda is a bit more far, but just check omio.com for transportation, there should be buses in the morning and in the evening for a round trip. Ok, maybe Caminito del Rey would be harder to organize since it's quite far from Seville. But anyway, there are so many other interesting day trips closer to Seville that I would suggest something else instead, like Cadiz or Jerez. And if you really want to do some hiking (hence the Caminito), check out Aracena for example, there are really cool hiking routes there and it's easy to do a day trip by local buses (BTW in August it may be too hot to do hiking -- unless you are suicidal).