Welcome to the wonderful world of paintball
Firstly you will find that different people may have very different opinions regarding set ups, and I would advise you to take everyones comments on board and work towards your own conclusion.
I've only been in the sport for 2 years but there are alot of VERY experienced guys and gals here on the forum who can offer you invaluable advice
I've got a set of I4s and I think they are fantastic, really comfortable and great visibility, the only problem some people have with them is they are smaller than most other masks around, which leaves your neck/chin more exposed depending on the size of your head. Alot of people go for Profits or E-Vents, but you would have to get information from someone else as I've never used them.
In my opinion a Mini is a great starter marker (depending on the generation, gen 2 or 3 are what you should look for). I started with one of these and I couldn't fault it, I used it for a year and never had any issues. Also you can usually pick one up for roughly £120-£150 on here
I've always used the same bottle so you would be better off taking advice from someone else on that.
As for the loader, I would avoid gravity fed and definitely try to stretch your budget a bit to get an electric loader. The Dye Rotor is one of the best on the market, easy to use, sleek design and quite a large capacity (and you can normally get one for £70-£80 on here). But again, other people may have better suggestions.
Where are you based? Or where are you looking at playing? You'll find that there are great, friendly people that make up this community and I'm sure anyone would be willing to advise you or possibly even let you try out equipment to help you make your mind up