I do not use premium, so you can reach the top without it. I just have a (hopefully) good plan on skills to hopefully have a chance to be a good concurrent to players with premium advantages and (maybe) worse skilling ^^'
On the other hand, I don't think I could get that far on world 2, because more people will know how to skill better. Automation and Regeneration premium give an advantage of ~60%-80% per day (not 50% as it seems, because there are some side effects). The advantage of the higher income premium is also more than 50% money, because items drop faster and are better, and thus give more money.
So if you combine these three pa`s on equal skilled players, you have a money advantage of over 100%, which makes town construction much more efficient. If you compare a premium and non-premium town with equal wisdom about skills, i think the premium town would grow at least 50% faster.
So the premium advantages are quite non-trivial. Though the first three premiums 'only' give advantages on player growth, the duel premium is a direct advantage in pvp which makes this premium imba. I do not understand, why one would pay for this. For me, it is not very glorious if I know that I win against another player, just because I payed for it. Well, then everybody should buy this premium for equal opportunities. Ok, then everybody could just ignore this premium, and it would be all the same ;-)
Concluding, for me the premium advantages can deform the game more than it may seem. On the other hand, I understand that anyone uses the first three premiums, especially the automation one (I'm thinking of buying this one), because it decreases the time spent on the game. If you are happy to find more items (as a single-player issue), the third one is also ok. I appeal to everybody to keep your hands off the duel premium because of the direct pvp advantage.
Last but not least: Keep in mind, this game is a beta! So the costs for premium are much to high. If you switch everything on, it is 100€ (for me it's in euro^^) a year per world! And this won't be the last world. As it is a beta i would also be cautious in paying premium, because there may come changes which might ruin your tactics you made. So you pay for a product that doesn't live up to what you thought was its promise. No offence at the developers. They should earn their money on what they are doing. Tribal Wars is one of the best browsergames I've ever seen. But those prices smell of rip-off for an unfinished product. On the other hand I'm happy that you can play it without paying anything, which makes me think about paying a little amount of money for an incomplete but promising product.
Just my few cents.. I know, the developers won't change anything^^ (well, maybe increase the prices or find new premium advantages / non-premium disadvantages
)