Since you mentioned steemit, i assume you mean the steemit platform. on steemit platform your best investment is in Steem power since it adds value to your voting power. you also should consider investing your time in content authoring by posting new content, making new comments, engaging with other steemians and curating others content.
With above approach you can get maximum from steem platform. i have noticed often people settling to acquire steem power and leaving it by delegating to someone and getting rewards. normally that earning is quite low since the other person is taking his cut also. you can increase that alot by posting your comment and engaging with the community.
in addition to the monetary benefits you will see your account growth as well. you will have alot more followers, alot of posts connections with similar interest so down the road you may not need your steem power as much as you need today to earn the same.
The downside of steem power investment is that you cannot withdraw / power down steem from steem power immediately, there is a 100 day waiting period and you get your withdrawl on weekly basis. you can stop the powerdown any time you want to.
if you share a figure of how much steem you are looking to invest i can help you with some of the calculations as well.