You don't need the top players to play well at all.
There are normally so many bargain players for absolute pennies who are very overpowered.
Infact, if anything, if you have really highly rated players you seem to get "scripted" against and end up more likely to lose games.
Only probably <0.5% of the FUT playerbase have very expensive teams tbh. If you just play gradually and build up...you will have a solid team within days/weeks, then in a couple of months, you'll have players like aguero/reus/lewandowski etc, just through playing in your spare time.
Personally i think it does make a lot of sense to chuck £32 or maybe even £64 at packs at the start if you believe you will play it all year round and the money won't be missed, but after that I think its fine to just let the coins build up from playing and invest wisely as the coins gather.
I think on release day I will probably chuck £64 at the packs, the game cost me £42, which i'll likely sell 6 weeks before the new one is out and get £20 back like the last two years. So in total if i spend £86 and play it for maybe 46 weeks of the year, then its actually costing me under £2 a week. If the game is actually good this year and doesn't have any massive issues with headers, then I feel its a damn bargain really! Fifa 14 was crap because of the crosses/headers but on Fifa 13 I must have played 2000 games. I'm really hoping fifa 15 is good

as i've really missed having a decent football game to play last year.