So the main thing to be aware of in HoD is maximizing your Colonial Points. Colonial Points for the most part come from ships and Naval Bases in
CORE provinces. Most of your points are going to come from ships. Ships now have a naval supply cost. You get naval supply points from building Naval bases, both in core and non-core provinces. You can only have one naval base per province. So:
Naval Supply Points -> Ships -> Colonial Points
Certain Ships (usually heavy ships) can only be constructed in Naval bases that are connected to your Capital by land or a strait. All ships also have a minimum naval base level they can be constructed in. You will want to like keep your Naval bases in constant production as the Dutch as you will probably only have 3 main bases to produce ships.
Here is the Wiki Link to
Colonization and to
Naval Units.
The Naval Units link has a table with Naval Point Cost / Colonial Point Cost / NPC:CP Ratio.
The ships that should be in your navy during the Scramble for Africa are: Ironclads, Monitors, Commerce Raiders, and Steamer Transports. Your wooden navy should be retired.Plus Ironclads have the best ratio for Colonial Points.
Don't build all heavy ships you need to have a mix or if you fight a war all your Heavy ships will be torpedoed by light ships and destroyed. The light ships act as screens as well as torpedo boots.
Your cost for colonial maintenance goes down if you have an adjacent colony.
So 80 or 100 will be your base cost for starting a protectorate. If you have competition you will need to keep adding Colony points until you get far enough ahead of your competitor or your competitor drops out. If your competitor is the UK you might as well quit as they have WAY more points to spend. The other option is to increase tensions in the colony and fight a colonial war for the colony. Once you successfully gain control of a territory you will drop down to the normal Protectorate maintenance cost and you can then upgrade to Full colony (for the normal points).
Getting inland in Africa is important because you can possibly pick up colonies without competition. If you get the correct territories you can block off access to other territories and colonize them later with no competition. Of course certain colonies are better like the ones with Tropical Wood or other RGOs so you have to weight your priorities.
You also need naval range as you used to before HoD. Taking Places like Sokoto and Ethiopia can be nice jumping off points for the scramble as the Dutch. Ethiopia can be taken with one war goal after Nationalism and Imperialism, even if they take Eritrea from Egypt. Sokoto you need to take one province in advance of Nationalism and Imperialism then you can use the Establish Protectorate CB on them (<4 Provinces.) Each of these Uncivs have territory adjacent to them that can be colonized before Colonial Negotiations is discovered as well. They also have decent populations. You can also connect the two with 2-3 inland territories that you shouldn't have much trouble colonizing at the start of the scramble as Egypt might be the only power adjacent and it is likely to still be an unciv and it is highly unlikely that if it is Civilized it will be a secondary power.
If you are lucky you can possibly pick on Portugal and grab stuff from them, as well as Oman. These give coastal colonies that can be used as Naval bases. Oman is an unciv and can be taken (usually with one war) after Nationalism and Imperialism. Portugal will likely have taken Lindi and brought them under 4 Provinces.
Of course as the Dutch you have access to Borneo and Papua New Guinea which have REALLY nice RGOs. Getting these should maybe your first move. Any of the other south Pacific islands save maybe Tahiti are a waste with just fish as an RGO.