Hi! 
Most brands of alarms you will find are very simple to use for a beginning fire alarm collection. Companies like Wheelock, System Sensor, Gentex, FCI, Federal Signal, and Faraday all make devices with little to no “surprises” in terms of their operation. Simplex, Fire-Lite, Notifier, Silent Knight, Edwards/EST, and Siemens/Cerberus Pyrotronics all make great products too, but at first you may run into issues like addressable or sync devices. Until you learn more about alarms to where you can determine which devices you can use, which is the majority of what they make, I would use caution with these manufacturers.
In terms of age, nearly all older devices will steer you clear of the issues mentioned above. If you are ready to start experimenting with a panel, please first refer to this topic: So you want to buy a FACP... .
If you want advice on a specific alarm to get, I personally would recommend starting with anything in Wheelock’s AS/NS/MT series. Very easy to find, affordable, and simple to operate. Have fun!