Elemental damage on your Kinsect is largely negligible, as your main source of damage is the glaive itself rather than the Kinsect. Due to this, choosing between a cutting or blunt Kinsect is also not really important, although some would lean towards a blunt Kinsect giving that you may be targeting the head a lot for red extracts.
Speed+ and Speed++ Nectars are important for increasing the Speed stat of your Kinsect. Speed+ Nectar can be gathered in the wild from plant resource nodes, although they have a relatively low drop rate, as well as purchased from the Wycoon. Speed++ Nectars can be found in abundance in G-rank expeditions, typically at plant resource points inside treasure areas.
Speed+ Nectar boosts Speed at the cost of Stamina. Thus, you'll typically want to use these Nectars before using any Stamina Nectars. Speed++, on the hand, boosts Speed and subtracts a point from all Element stats. If you are intent on using Element Nectars to get an elemental Kinsect, you'll want to use Speed++ Nectar before working on the Element stat.