How much should I invest in SEO campaign, and what can I get?

To be honest, there is no set package that can fit into all the website. What deliverable you would have required, based on it, pricing always set for the campaign. Most of the SEO provider companies placed pre fixed pricing on their website, and they try to convince the visitors to purchase them.

You Could Be Banned

Internet Statistic shows, billions of peoples are using the internet to search the websites for their requirements. The more visible you are, more responses you will get. Websites are like an online offices, and it should be well-designed, and architect to attract the customers. If you do not make it happen, your website will fall behind the line. If you are new to this web-world, let me guide you to stay protected from penalties.  

Examine SEO consultants, before engaging them to help you with your SEO

There are lots of SEO companies and freelancers ready to reach you to offer SEO services. However, be sure to examine their knowledge before asking them to help you.  If you hire a worst partner, the result will be same (No wonders). Some partners may produce the result, but consistency is important.  They don't own Google, and no one can give the guarantee on its algo updates.

Solving the Pogo stick problem

Most of us don't know about the Pogo stick problem. This is the issue which really can affect your current ranking.Your website is coming on the top for most of the search terms. You're getting huge traffic, probably most of them are your potential customers. However, have you ever noticed your bounce rate? Is it constant, or decreased, increased....?

One Languaze One Website Or Two Languaze One Website

What is good? Different website for different languaze or a multilinguist website is better idea!!

If you've enough time to market your each website, than I would suggest to use different website for each languaze. It will also help you to build and grow your local market too.

You need enough content in different languaze to market your websites. You can't use same content for every website by only translating it to your desire languaze. It's simply called duplicating the contents, a unprofessional way to market your website.

It's also help you to minimize your website on-page and on-site issues. With a Multilinguist website you can't fix all the technical error as few of them are really helpful. Mark up validation may show you numbers of error, however it's not a ringing bell.

The next factor is linking; what strategy you need to follow to build your links? You've a non-English site and you're targeting the SE's based on the region, only because you've used specific languaze to reach your target audience. You can develop different contents to generate the links and specially you need anchor text with specific languaze. This'll reduce your campaign time limit.

Considering the languaze, you can target the keywords. I mean, this is really wise to target the local keywords to market your offerings. You can't go for only English keywords, when you've a non-English website.

Hence, I'll recommend to use different website for different languaze only when you've enough time to market it.