How can I ensure my site will not have bugs before it gets hit with massive traffic?

If I was just starting out, I'd consider learning Meteor (https://www.meteor.com/). It's just entered version 1.0 and after working with it for a little less than a year I do have some issues with it but it still makes for a very solid framework that gets you up and running very fast. You would only need to learn Javascript, and you can slowly work your way towards nodejs from there (which Meteor is based on) if you want to, or you could get the basics down and focus on learning design if you prefer.

Yes Wix supports a mulitude of APIs to used for various fetch calls for your web pages. If you already have to API's in mind you can venture off within you WIX code to integrate within your application's processes. There shouldn't be any complications getting this done. Please see the link below for more information https://www.wix.com/code/home/api

https://www.filepicker.io/ is the best thing that you can integrate with this app which suits your requirement. If you are the owner of the app, you can integrate it very quickly. If not, you can suggest the app owner to do it Feel free to call me if you need more clarification. I am consulting architect for few companies in US and India on mobile, web and windows/linux/mac apps.

Usually Programmers are only slow when they don't know how to solve a particular problem. So they will spend a lot of time researching and a lot of trial & errors to solve a problem. It is important that before you engage a programmer on a project, you break down the entire project into simple, easy to understand modules. Let him give you an estimate of how many hours he will require to complete each of the modules. Example: a typical site will have a login module, registration, My account, profile etc. So let him estimate how much he will require to do the login. You can go even detail here. (e.g. how much extra time if you were to implement Facebook/Twitter Login?). Once he start developing, track his progress closely and make sure he is following his given timeline. If he goes over his budgeted time on a module, talk with him and see what went wrong. It is often seen that they may be wasting their time on something very insignificant that you may have asked him to implement, but you can totally go by without it too. So by understanding what is taking longer time, you will be able to prioritise things better. You definitely need some tools to get this done. Google Spreadsheet or Excel works just fine. But if you don't mind spending a few bucks there are many agile project management tools that you might look into. Here is a list, google them all and sign up for trials: * AgileZen * Agile Bench * Assembla * AssiTrack * Blossom * Basecamp * Breeze * DoneDone * Eidos * Fogbugz * GreenHopper * Jugggla * Kanbanpad * Pivotal Tracker Or the reason why he is slow can be purely non-technical. Sometime your developer may don't share the same level of enthusiasm as you about the idea that you are working on. They often don't often see the "bigger picture" (since you don't share everything with them explicitly). If you can somehow get them excited about what he is a part of, it will work like a drug :) He will work day and night without questioning you. But you need to work equally as hard as him. The moment he sees that you are the boss and he is just the guy doing work for you -- his mentality will shift from being part of something to being the low paid developer. Ultimately its all about motivation and making him a part of your venture. After all he deserves it, if he is really playing a crucial role in the entire development.

Well this totally depends what your MVP is? What's the functionality? I'd suggest something like http://www.squarespace.com/ our designers with very little technical knowledge have had great success with this. Another option if it's just for demos/feedback is to use something like http://www.invisionapp.com/ for rapid prototyping.