Yes, with you because signature campaign is best way to get more bitcoins. But there are a few official websites of bitcoin on internet to earn bitcoin. Especially gambling websites. Where you can get a lot of bitcoin instead signature campaign but the things is that you should have more knowledge about online gambling sites. Then you can easily win the games in bitcoin gambling websites.

to me i think the only way through which we can earn bitcoin without any investment is a signature campaign, i think through signature campaign we can earn money without any investment.

Well as like any other bitcoiners, you could earn BTC by offering your services and joining bounties, campaigns and some give a way job in the services section. Though, Rank plays a big role in this community. Normally, Some of Campaigns today accepts Jr. Member and Up. Just be active here but be cautious when posting, don't do burst posting as you can be tagged as a spammer. A good start up is to post constructive one, don't post for the sake of posting.

If you are to offer your services do make a thread at the services section and be detailed:
1. Service Offered
2. Skills and experience
3. Portfolios *If ever*
4. Rates *Be rational*
 

Activity on this forum, you can join the campaign signature. You have to be patient to get the reward after the operation.

you can get 300 free doge for joining tux exchange and trade up

At this time have started hard to make the amount of bitcoin sustainable without investment, how to get way by not using investment ??

Participate to some signature campaign. You can earn a lot of btc there.

Im not in the position to tell you this since im also new to the bitcoin world but upon hours of research, this is some of what i have learned. As most people say, right now it is hard to earn bitcoin. I was advised by a friend to look no further, stay active and post content on this forum i was told to gain rank. Ranking is a long process since we have to post regularly and not just posting something for the sake of posting. Anyway after you rank up you/we have join campaigns then when you earn coins from campaign you can try and trade. Buying low and selling high, much like on stock market, that is something i have experience on that is also another reason why i got involved in bitcoin. Other source is faucets but I haven't tried it another thing is gambling and mining haven't tried it as well. Anyway i wish you/us luck on this world and hope we earn and learn in the process.

Joining a signature campaign is not the only way to earn a bitcoins. If you will be opening your mind in these forum, you can see a lot more.
Also, you can make your earnings from signature campaign as your asset, make it an investment to ICOs.