Native app for what device? But generally, given all hardware specs equal, performance will always be better on a dedicated box because hardware is installed locally. You only use cloud if you need relatively easier redundancy and scalability.
So for lower costs, it would be better to start off with a dedicated box with CDN? Cause I'm not liking the cloud setups at low ram, because if I get a dedicated, it will be ready for a sudden spike of users say first week 100-300 concurrent users everyday, then the next week it gets higher, I want the server to be able to handle high traffic, do you think a setup with a bunch of low cloud nodes say 4 cloud servers at 1GB ram a piece with 10GB of space, and 1 cloud server specifically for mysql would be able to handle 1000 concurrent daily users who upload and share photos and videos? or would a 2 cheap dedicated servers with high ram be doing better? I'm really new to this, cause I don't want my developers to release the app and the server setups for the beginning isn't ready, we have a huge fan base for anticipation of the app release say 5000 fans, so when the app comes out, they will for sure use it ASAP.
If you're not really familiar with server setups, I think you're better off using PaaS providers like Heroku, AppFog, Pagoda Box, etc. They are designed for app developers who don't want to meddle with server administration. They are scalable and you don't have to worry much about technicalities.
Sorry for so many questions, two cheap dedicated servers with 8gb ram a piece and CDN would be better right? Which would reach like $260-$300 a month with 2 servers loud balanced with 8GB ram, and then CDN file storage for the files like 1TB.
As far as hardware specs go, no one can tell exactly what you need until there are actual users (or you can do some load testing before launch) but having at least two load balanced servers is a good start. You can just scale as you see fit.