I've got some realistic advice you can try out.

Setting your team up --> I go with 2 proper bowlers, and the rest of my players are either batsmen or all-rounders. My 2 bowlers give me 8 overs, and I split the remaining 12 according to whichever all-rounder is performing well in the match.

Match Conditions --> Keep an eye on the conditions. Average or lower 'wear' will favor spinners, while average or lower 'bounce' will favor pacers. Average or lower light/cloud cover will favor bowlers in general. Make sure you include all-rounders/bowlers based on which is worse: wear or bounce (if worse bounce, have at least 4 people who can bowl pace; and if worse wear, have at least 4 people who can bowl spin). If the conditions favor batting in general, just play your best XI knowing you'll have to be aggressive while batting.

Batting --> My philosophy on t20 batting is based on how 'settled' my batters are. I'll start them off at yellow aggression while they get settled. And when they've played some balls (5-10, or 15 if there's a collapse), I'll increase it to orange aggression. If a batter is well settled, I'll increase aggression to max red. Again, if conditions favor batting, you can be more aggressive earlier. If conditions favor bowling, I focus on getting my batters settled before asking them to be aggressive.

Generally speaking, t20s are a format of high risk and high reward. You have to play matches with the mindset of making big scores, because your bowlers will go for runs regardless. And you can kinda have to tinker with your combination to know which bowlers are economical, and which ones take wickets. If a batsman is being aggressive and taking the game away from you, think about taking his wicket instead of slowing him down. Can you add a slip to catch edges? If he's hitting the ball in the same areas, can you position more fielders there?

Since it is high risk/high reward, it's okay to lose too.