I tried this and that, but they were all a waste of time.
I experimented with lots of different things, but they were all useless.
詳しいシチュエーションがわかりませんが、次のような言い方ができると思います。
ーI tried this and that, but they were all a waste of time.
「あれこれ試したが、どれも時間の無駄だった」
to try this and that で「あれこれ試す」と言えます。
a waste of time で「時間の無駄」
ーI experimented with lots of different things, but they were all useless.
「いろいろ試したが全て無駄だった」
to experiment with lots of different things で「いろいろなことを試みる」
useless で「無駄な・役に立たない」
ご参考まで!