Warning, ye olde religious folks, thou may becometh triggered.
Okay, I want to get one thing straight here: being a Christian means having a personal relationship with God. Having a personal relationship with anyone requires that you spend time with all other parties in said relationship. So, with all of that being said, if you claim to be a Christian, you have to actually get to know Christ.
I hate to be the bearer of bad news, (Actually not really, but I think would prefer the title "harbinger of truth.") but just reading the Bible and listening to what your pastor says is not enough. You have to actually spend time in the presence of God and pray. And when you pray, listen to what God has to say--just like you would in any other conversation.
Now, it is both good and extremely important to read the Bible because that is God's Word, and it will help you get to know God better. Reading the Bible will also help you get better in general; however, it is not the only way to become acquainted with our wonderful, heavenly Father.
"All scripture is God-breathed [given by divine inspiration] and is profitable for instruction, for conviction [of sin], for correction [of error and restoration to obedience], for training in righteousness [learning to live in conformity to God's will, both publicly and privately--behaving honorable with personal integrity and moral courage]; so that the man of God may be complete and proficient, outfitted and thoroughly equipped for every good work." II Timothy 3:16-17 AMP
The Bible even tells us to pray at all times, without ceasing. In the New Living Translation (NLT), I Thessalonians 5:17 simply says, "Never stop praying." That being said, setting aside 10-15 minutes to pray is an awesome way to start, but you will eventually come to the point where those few minutes are not going to be enough. As you continue to grow in your Christian walk, the amount of time you spend in your prayer closet should increase as well.
In all honesty, there is no specific formula or amount of time one should pray. God is neither confined to nor constricted by time but is instead free to flow in and out of time as He pleases. It just isn't right for us to make a 10-15 minute box--or even a 60 minute box--and say, "Okay, God, this is the time I'm giving you to work and to talk to me. Get in and get to it." Or even worse, we set aside that time and then just spend the entire time talking or complaining about us and don't even let God get a word in edgewise.
Please don't misinterpret what I'm saying. I am not saying that if you don't spend 40 days on top of a mountain praying to God like Moses did, then you're not really a Christian. But so many of us have just gotten into this habit and have been believing this lie that God only deserves an hour or less of our time, or the lie that you have to spend "x" amount of time praying for "y" to happen. Both of those are simply not true.
There isn't a formula, a practice, or a ritual that makes God come in some magical way. God isn't a magician, and you can't just pull Him out of a hat either. He's not a vending machine, so 10 minutes in prayer won't get you this certain miracle and 20 minutes won't get you that other one. You cannot dictate or pick and choose how God works and what God does. He is God. We are not.
All you can do is get to know Him as much as you possibly can. Develop a habit of praying daily and reading the Bible, God's word, on a regular basis. Then see how much your life changes. If you're wanting a miracle, waiting to get to that next level, or begging for a breakthrough--whether spiritually, financially, or any other way--stop asking for it on your terms. Instead, let God be God. I can assure you that you will be amazed at what He can (and will) do.
"My purpose in writing is simply this: that you who believe in God’s Son will know beyond the shadow of a doubt that you have eternal life, the reality and not the illusion. And how bold and free we then become in his presence, freely asking according to his will, sure that he’s listening. And if we’re confident that he’s listening, we know that what we’ve asked for is as good as ours." I John 5:13-15 MSG