In IT by career here. Apple users liked to brag for years that their devices were superior because they just "don't get viruses", malware or the like. They like to think that iOS was more secure than MS. The reality however is they weren't targeted even close to the same capacity since Microsoft had, and still has an immense presence over iOS. Per the iPhone/iPad, Apple is gaining, which has also garnered the attention of bad people so you do see it today. The good news is Apple does a pretty good job in securing, if not limiting the applications and vulnerabilities of their mobile devices. The bad news is, you can still get malware or viruses that could release private info.
The biggest issue you will have is with the Apps you download. Just look for Apps with MANY reviews. If you see an App that only has 10, then you don't want it. You would be surprised how many apps track your info and report it back. Stay away from the Facebook games, or many free games for that matter and do read the privacy agreements. Also, just like a PC, pay attention to where you browse, what you click/allow, and don't click email links you are unsure of. It's not something you need to be paranoid of, but instead just use a little common sense and you will be fine. Just don't be that guy who has a warrant for his arrest and was amazed at his good fortune in being selected to win a vacation to Hawaii...
Keep your hotspot off unless you are using it at that moment, and ensure your bank apps or the like are not set to logon automatically. To be honest, your biggest concern is losing the device, so just ensure you have a passcode and a good backup. You could setup "find my iPhone", which would prevent someone from using your phone if they stole it/found it. Honestly though, I'm not sure why anyone would care. If it's gone, it's gone for you and having your GPS enabled all the time is more of a risk than someone stealing my phone, wiping it and using it. (They can wipe it even with a passcode, they just can't get to your data).