It depends on where you (i.e. your devices) are coming from. I'll assume USA.

Type F is the most common type of socket you'll find here. It's compatible with type C and E plugs as well.

AC voltage is 230 V at 50 Hz. Almost all portable electronic devices these days are universal (i.e. 100-240 V, 50/60 Hz) but check the label on the power adapter for your device just in case.

SKROSS adapters are the most popular around here and are probably the first ones you would encounter at the airport. They are pricey, versatile and high quality. But any cheap adapter from Amazon will work. Things to consider:

• Size: The most important factor, since you will be dragging it around the world.
• Versatility: If you tend to visit multiple countries with different plug types during a single trip, consider an adapter that supports all the types you need. These tend to be bulkier and more expensive so otherwise prefer the simplest, smallest and cheapest ones.
• Safety/Insulation: If you need to use high-powered, especially heating devices that lack double insulation, consider buying an adapter with ground connectors. It has the third hole for the Type B US plug and has the metal side connectors of the Type F EU plug. This will protect you from electrocution if your device malfunctions.
• Quality: I've had some cheap adapters that have trouble staying in the wall and keep falling out. Read the reviews and see if there are complaints.

Something like this should be fine for any device supporting the local voltage (looks small, safe and durable).

In contrast the cheap-o ones look like this but they are not grounded and often have trouble staying in the wall if you tend to yank the cord of your charger.

If you REALLY need to convert voltage as well, there are step-down converters on Amazon for like $30-50 but they are heavy and a pain to drag along.

Hair dryers yes, almost always. Not sure about USB ports but I'd assume many do these days. So same as in the US I guess. And if they don't, you can easily find a local plug for your USB cable.

Note that some of the more expensive travel adapters also have USB ports. If you're spending on a transformer, it might make sense to choose one with USB support.

When choosing a transformer, notice that the cheaper ones have a power limit. Check the label on your hair straightener to see its wattage. A good guess would be a bit under 200 W, so you'd need a transformer with capacity higher than that.

If your hair straightener isn't too dear to you, it might be easier/cheaper to just buy a new one, possibly one that supports multiple voltages (if they exist).

My transformer recommendation after 5 mins research is the one I linked earlier. It's the highest rated one that works with 100 V heating devices. Some models are single unit that plugs straight into the wall but they are so bulky that they won't fit in sockets that have small clearance around them. This model has a cord so it can fit anywhere. Also the EU plug is detachable so you can carry that small part in your pocket if you need to charge your phone away from the hotel.

Edit: Here's a cheaper option but max 230 W and a bit bulkier plug pieces.

Edit 2: Also some hotels provide 120 V power outlets so ask them about their amenities! It might save you from this trouble :)