Absolutely! It seems like you are planning a fantastic trip to Italy and Spain. Here are some travel tips for your journey:

Best Time to Visit:
The best time to visit Italy (Rome, Florence, Venice) and Spain (Barcelona, Madrid) is during Spring (April to June) or Autumn (September to October). The weather during these periods is mild and comfortable.

Route and Accessibility:
In Italy, you can start from Rome, then move northward to Florence and then Venice. Trains are the best option to travel between these cities.
For Spain, direct flights from major Italian cities to Barcelona are available. From Barcelona, you can reach Madrid by high-speed train.

Altitude and Acclimatization:
These cities are located at lower altitudes, so acclimatization is not typically an issue. However, ensure to rest well and stay hydrated.

Accommodation and Booking:
Hotels and Airbnb are readily available in all these cities. However, book in advance to secure better deals especially if your travel coincides with peak tourist season.

Clothing and Essentials:
Pack for variable weather with layers - clothes suitable for warm days and chilly nights. A good pair of walking shoes is a must since these cities are best explored on foot. Do not forget necessary travel adapters for your electronic devices because socket types in Europe might be different from your home country.

Health and Safety:
Ensure your travel insurance covers illness or accidents. Maintain awareness of your belongings as pickpocketing can be an issue in tourist areas. It's also a good idea to carry a basic first aid kit.

Local Etiquette and Respect:
Respect local customs and traditions. Particularly while visiting places of worship, dress modestly, and maintain silence. In Spain, try to take up the local practice of a siesta (afternoon rest). Remember to tip in restaurants and cafes; a small amount is appreciated.