Let's talk about a paladin
If you train your distance from "0" to 80 in a normal day, without double experienceand with a conventional dummie you would spend 2,750 Tibia Coins
Why skills up to 80? Simple, all you can kill alone, you don't need more than 80 skill
1° 30 - Tibia Coins
2° 45 - Tibia Coins
3° 90 - Tibia Coins
4° 180 - Tibia Coins (You can buy up to 5, but in this case, it does not help us because you only have 4 hours to play in tournaments)
Third Prey - 900Tibia Coins
Prey Wildcard x20 - 200 Tibia Coins
So ... speaking of an approximate as you mention, the cost is: 2750 + 30 + 45 + 90 + 180 + 900 + 200 = 4195 Tibia Coins approximate
or 1,445 without training your skills.
This calculation is only a personal opinion, I am not a regular tournament player, but try to gather true information and make an approximate calculation.
Have Fun !