There are 4 general categories of cryptocurrency:
Those that easily mine on ASIC, such as Bitcoin and other SHA256 coins. As such, ASICs outperform anything else and are the only way to go. That means a big investment, free electricity, or both is needed to get a good profit.
Those that are ASIC resistant but not GPU resistant, such as Curecoin, Foldingcoin, and a number of other cryptocurrencies. With ASICs not being an option, GPUs become the miner of choice. Note that developments could make some coins in this category, such as Litecoin, no longer ASIC resistant. I personally like Curecoin and Foldingcoin because they can be merge mined and help find cures for cancer. If they cause an ASIC to be developed (unlikely given how diverse the task is), it would be a huge benefit for society.
Those that are ASIC resistant and GPU resistant, such as earnhoney. CPUs are then the only way to mine it, and depending on the coin, it can be mined on either desktop or mobile CPUs, the latter being more efficient but usually more expensive per computing power. I say "usually" since it is possible to find cheap smartphones (have to wait for a sale) that work out to a lower cost per MIPS than a desktop CPU along with a higher efficiency. However, with the way things are, even $20 smartphones aren't good investments nowadays.
And then there are altcoins that rely on hard drive storage for mining, the idea being that it is orders of magnitude cheaper to store tables used to calculate hashes than to recompute them every time. Burstcoin, Storj, Sia, and one new coin are currently in this category. Efficiency is on the same level as smartphone coins, but it is far easier to find other uses for a few TBs of HDDs as opposed to 10 or so cheap smartphones.
Thank you for your time to explain this for me.
What's your suggestion on wich miners to go for ?
A series of same types to speed up mining a handfull coins or a series of different miners able to mine all sorts of algorithms ?
Note that i can make an investment arround 4k dollars for start up. If needed i can expand in future with profits generated from mining.