The most important factor in your application is proof of ties. So since your first application was refused, you want to focus on showing stronger proof of ties to your home country. To prove employment, provide a letter from your employer confirming you are employed and also indicating that they know you will be going for a visit to Canada (and what the planned dates of your trip are). Also provide pay stubs to show your salary payments. For your own proof of funds, provide a bank statement. Hopefully you have funds of at least $10K to show. If you have less, there's not much you can do about that.
In general, you want to emphasize ties to your home country and not emphasize ties to your fiance in Canada. If you provide too much evidence in your application for your fiance, this will often make IRCC concerned you have plans to stay long term.
It's often a good idea to provide an itinerary of what you plan to do while you are visiting Canada (you would include this in your cover letter or your fiance can include this in his invitation letter).
Good luck with your second application.