First you need to understand how reputation works:
Your reputation on Steemit is increased by other users upvoting your posts. (also note that downvotes decrease your reputation).
For each of your posts the reward shares of the votes made (i.e. your share of the reward pool) is added to your reputation so that it increases. (the rshares from flags are deducted from your reputation).
Reputation level for a new user is 25. It is more difficult to move from one reputation level to the next as your reputation increases as it is a logarithmic scale.
Now how to improve your reputation:
The normal approach is to create good posts for which you obtain lots of upvotes. Easier said than done! However there are some platforms such as DTube and DLive with large delegations on which even new Steemians can be rewarded with high upvotes if they produce good quality and original posts.
The short cut approach is to use bid-bots. Just make sure that your post is of sufficient quality and not plagiarised so that you do not join the blacklist. When you pay for a bid-bot you receive upvotes which also increase your reputation. So you can in fact pay for a higher reputation by churning your rewards through the bid-bots, using the rewards from each post to pay for the next set of bid-bots.
Reputation is not a great system on the Steem blockchain and there have been many approaches proposed to improve it. I would recommend that if you are running a project, reputation is not the best measure on which to found any conclusions.