Trying out Rising Star AD

In the game Rising Star it is possible to buy Ads. Is it good? Is it bad? OR????

First test

Some weeks ago Rising Star was sponserd me with 3 booster packs. The contest was pretty easy and I did get free Ads at the game.
It was awesome - 30-40 person joined the contest every day in three days.

I really think it was because of the Ad because next day I had a contest without Ad with only 5-8 persons joined.

Second Test

Yesterday I started a new contest. You can win 2 booster Packs in Rising Star. This time the contest is little more hard to join (you need to play a Kahoot-quiz).
I used 5000 Starbits and pay 7 starbits per view. So about 800 persons should see the Ads.

Time: It took about 45 miutes to spend the first 2500 Starbits. I notice no more activity at my blog.
Later on the starbits was out - and no comment.

BUT - it can be that my contest was to hard to join.

I think Ad can be very powerful - but it has to be Right Ads to Right Product. This time something was wrong.